gemini_adk_fluent_rs/spec/
project.rs

1//! Generate a project around a [`SessionSpec`] in Rust, Python or Go.
2//!
3//! The spec stays the agent: model, instruction, conversation, tool
4//! declarations and tests, as data in `agent.json`. A generated project adds
5//! what data cannot carry, the tool implementations, as one typed function
6//! per tool the spec declares as a mock. Each function returns the spec's
7//! mock response until its body is replaced, so a fresh project behaves
8//! exactly like the spec does offline.
9//!
10//! - **Rust** registers the functions in process with
11//!   [`SpecResources::implement`](super::SpecResources::implement) and runs
12//!   the session itself.
13//! - **Python** and **Go** serve the functions as an MCP tool server over
14//!   stdio. The project's `agent.json` points each of those tools at the
15//!   server through its `mcp` binding, and any runtime that loads the spec
16//!   (`adk spec run`, the runtime server) calls them there.
17//!
18//! In every language the declaration in `agent.json` is what the model sees,
19//! and the spec's `set_state` and `save_response_as` still apply.
20
21use std::fmt::Write as _;
22
23use serde_json::Value;
24
25use super::{SessionSpec, SpecModality, ToolSpec};
26
27/// The language of a generated project.
28#[derive(Debug, Clone, Copy, PartialEq, Eq)]
29pub enum ProjectLanguage {
30    /// A Cargo binary that runs the session with in-process tools.
31    Rust,
32    /// An MCP tool server using the official `mcp` package.
33    Python,
34    /// An MCP tool server using the official Go SDK.
35    Go,
36}
37
38impl std::str::FromStr for ProjectLanguage {
39    type Err = String;
40
41    fn from_str(s: &str) -> Result<Self, Self::Err> {
42        match s.to_ascii_lowercase().as_str() {
43            "rust" | "rs" => Ok(Self::Rust),
44            "python" | "py" => Ok(Self::Python),
45            "go" | "golang" => Ok(Self::Go),
46            other => Err(format!(
47                "unknown language '{other}': use rust, python or go"
48            )),
49        }
50    }
51}
52
53/// Where a generated Rust project gets the SDK crates.
54#[derive(Debug, Clone, Default, PartialEq, Eq)]
55pub enum SdkSource {
56    /// crates.io, at this SDK's version.
57    #[default]
58    Registry,
59    /// A local checkout of this repository, by path to its root.
60    Path(String),
61}
62
63/// Options for [`SessionSpec::to_project_with`].
64#[derive(Debug, Clone, Default)]
65pub struct ProjectOptions {
66    /// Where a Rust project gets the SDK crates.
67    pub sdk: SdkSource,
68}
69
70/// One file of a generated project.
71#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize)]
72pub struct ProjectFile {
73    /// Path relative to the project root, with `/` separators.
74    pub path: String,
75    /// File contents.
76    pub contents: String,
77}
78
79impl ProjectFile {
80    fn new(path: &str, contents: String) -> Self {
81        Self {
82            path: path.to_string(),
83            contents,
84        }
85    }
86}
87
88/// The command a Python project's `agent.json` uses to start its server.
89pub const PYTHON_TOOL_SERVER: &str = "python3 server.py";
90/// The command a Go project's `agent.json` uses to start its server.
91pub const GO_TOOL_SERVER: &str = "go run .";
92/// The Go MCP SDK version generated projects require.
93const GO_MCP_SDK: &str = "v1.8.0";
94
95impl SessionSpec {
96    /// A project in `language` that runs this spec. See the
97    /// [module docs](self) for what each language generates.
98    pub fn to_project(&self, language: ProjectLanguage) -> Vec<ProjectFile> {
99        self.to_project_with(language, &ProjectOptions::default())
100    }
101
102    /// [`to_project`](Self::to_project) with options.
103    pub fn to_project_with(
104        &self,
105        language: ProjectLanguage,
106        options: &ProjectOptions,
107    ) -> Vec<ProjectFile> {
108        let tools = stubbed_tools(self);
109        match language {
110            ProjectLanguage::Rust => rust_project(self, &tools, options),
111            ProjectLanguage::Python => python_project(self, &tools),
112            ProjectLanguage::Go => go_project(self, &tools),
113        }
114    }
115}
116
117/// The tools a project implements: those with neither an HTTP nor an MCP
118/// binding, i.e. the spec's mocks.
119struct ProjectTool {
120    declaration: ToolSpec,
121    skill: Option<String>,
122    ident: String,
123    type_ident: String,
124}
125impl std::ops::Deref for ProjectTool {
126    type Target = ToolSpec;
127    fn deref(&self) -> &ToolSpec {
128        &self.declaration
129    }
130}
131
132fn stubbed_tools(spec: &SessionSpec) -> Vec<ProjectTool> {
133    let declarations =
134        spec.tools
135            .iter()
136            .map(|tool| (None, tool.clone()))
137            .chain(spec.skills.iter().flat_map(|skill| {
138                skill.tools.iter().map(move |tool| {
139                    let mut declaration = tool.tool.clone();
140                    if let Ok(parameters) = super::skills::task_parameters(tool) {
141                        declaration.parameters = parameters;
142                    }
143                    (Some(skill.name.clone()), declaration)
144                })
145            }));
146    let mut identifiers = std::collections::BTreeSet::new();
147    let mut types = std::collections::BTreeSet::new();
148    declarations
149        .filter(|(_, tool)| tool.http.is_none() && tool.mcp.is_none())
150        .map(|(skill, declaration)| {
151            let stem = skill.as_ref().map_or_else(
152                || declaration.name.clone(),
153                |skill| format!("{skill}_{}", declaration.name),
154            );
155            let base = snake(&stem);
156            let mut ident = base.clone();
157            let mut type_ident = pascal(&ident);
158            let mut suffix = 2;
159            while identifiers.contains(&ident) || types.contains(&type_ident) {
160                ident = format!("{base}_{suffix}");
161                type_ident = pascal(&ident);
162                suffix += 1;
163            }
164            identifiers.insert(ident.clone());
165            types.insert(type_ident.clone());
166            ProjectTool {
167                declaration,
168                skill,
169                ident,
170                type_ident,
171            }
172        })
173        .collect()
174}
175
176fn scoped_server(server: &str, skill: Option<&str>) -> String {
177    skill.map_or_else(
178        || server.into(),
179        |skill| format!("{server} --skill {skill}"),
180    )
181}
182
183/// `agent.json` with each stubbed tool bound to `server`.
184fn spec_bound_to(spec: &SessionSpec, server: Option<&str>) -> String {
185    let mut spec = spec.clone();
186    if let Some(server) = server {
187        for tool in &mut spec.tools {
188            if tool.http.is_none() && tool.mcp.is_none() {
189                tool.mcp = Some(server.to_string());
190            }
191        }
192        for skill in &mut spec.skills {
193            for tool in &mut skill.tools {
194                if tool.tool.http.is_none() && tool.tool.mcp.is_none() {
195                    tool.tool.mcp = Some(scoped_server(server, Some(&skill.name)));
196                }
197            }
198        }
199    }
200    let mut json = serde_json::to_string_pretty(&spec).unwrap_or_else(|_| "{}".into());
201    json.push('\n');
202    json
203}
204
205fn project_name(spec: &SessionSpec) -> String {
206    let name: String = spec
207        .name
208        .chars()
209        .map(|c| {
210            if c.is_ascii_alphanumeric() {
211                c.to_ascii_lowercase()
212            } else {
213                '-'
214            }
215        })
216        .collect();
217    let name = name.trim_matches('-').to_string();
218    if name.is_empty() || name.starts_with(|c: char| c.is_ascii_digit()) {
219        format!("agent-{name}").trim_end_matches('-').to_string()
220    } else {
221        name
222    }
223}
224
225fn mock_response(tool: &ToolSpec) -> Value {
226    tool.response
227        .clone()
228        .unwrap_or_else(|| serde_json::json!({ "ok": true }))
229}
230
231// ── Parameters ──────────────────────────────────────────────────────────────
232
233#[derive(Debug, Clone, Copy, PartialEq, Eq)]
234enum Kind {
235    Str,
236    Int,
237    Num,
238    Bool,
239    List,
240    Object,
241    Any,
242}
243
244struct Field {
245    json: String,
246    kind: Kind,
247    required: bool,
248    description: Option<String>,
249    choices: Vec<String>,
250}
251
252/// The top-level parameters of a tool, required ones first.
253fn fields(tool: &ToolSpec) -> Vec<Field> {
254    let Some(schema) = &tool.parameters else {
255        return Vec::new();
256    };
257    let required: Vec<&str> = schema
258        .get("required")
259        .and_then(Value::as_array)
260        .map(|r| r.iter().filter_map(Value::as_str).collect())
261        .unwrap_or_default();
262    let mut fields: Vec<Field> = schema
263        .get("properties")
264        .and_then(Value::as_object)
265        .map(|props| {
266            props
267                .iter()
268                .map(|(name, prop)| Field {
269                    json: name.clone(),
270                    kind: kind_of(prop),
271                    required: required.contains(&name.as_str()),
272                    description: prop
273                        .get("description")
274                        .and_then(Value::as_str)
275                        .map(str::to_string),
276                    choices: prop
277                        .get("enum")
278                        .and_then(Value::as_array)
279                        .map(|e| {
280                            e.iter()
281                                .filter_map(Value::as_str)
282                                .map(String::from)
283                                .collect()
284                        })
285                        .unwrap_or_default(),
286                })
287                .collect()
288        })
289        .unwrap_or_default();
290    fields.sort_by_key(|f| !f.required);
291    fields
292}
293
294fn kind_of(prop: &Value) -> Kind {
295    let ty = match prop.get("type") {
296        Some(Value::String(t)) => t.as_str(),
297        Some(Value::Array(types)) => types
298            .iter()
299            .filter_map(Value::as_str)
300            .find(|t| *t != "null")
301            .unwrap_or(""),
302        _ => "",
303    };
304    match ty.to_ascii_lowercase().as_str() {
305        "string" => Kind::Str,
306        "integer" => Kind::Int,
307        "number" => Kind::Num,
308        "boolean" => Kind::Bool,
309        "array" => Kind::List,
310        "object" => Kind::Object,
311        _ => Kind::Any,
312    }
313}
314
315/// `snake_case` identifier characters from any name.
316fn snake(name: &str) -> String {
317    let mut out = String::new();
318    for (i, c) in name.chars().enumerate() {
319        if c.is_ascii_uppercase() && i > 0 && !out.ends_with('_') {
320            out.push('_');
321        }
322        let mapped = if c.is_ascii_alphanumeric() {
323            c.to_ascii_lowercase()
324        } else {
325            '_'
326        };
327        if mapped != '_' || !out.ends_with('_') {
328            out.push(mapped);
329        }
330    }
331    if out.is_empty() || out.starts_with(|c: char| c.is_ascii_digit()) {
332        out.insert(0, '_');
333    }
334    out
335}
336
337fn pascal(name: &str) -> String {
338    let mut out = String::new();
339    for part in snake(name).split('_').filter(|p| !p.is_empty()) {
340        let mut chars = part.chars();
341        if let Some(first) = chars.next() {
342            out.push(first.to_ascii_uppercase());
343            out.extend(chars);
344        }
345    }
346    if out.is_empty() || out.starts_with(|c: char| c.is_ascii_digit()) {
347        out.insert(0, 'T');
348    }
349    out
350}
351
352fn one_line(text: &str) -> String {
353    text.split_whitespace().collect::<Vec<_>>().join(" ")
354}
355
356/// A JSON string literal, which is also a valid Rust, Python and Go string
357/// literal for the characters JSON escapes.
358fn quoted(text: &str) -> String {
359    serde_json::to_string(text).unwrap_or_else(|_| "\"\"".into())
360}
361
362// ── Rust ────────────────────────────────────────────────────────────────────
363
364const RUST_KEYWORDS: &[&str] = &[
365    "as", "async", "await", "break", "const", "continue", "crate", "dyn", "else", "enum", "extern",
366    "false", "fn", "for", "gen", "if", "impl", "in", "let", "loop", "match", "mod", "move", "mut",
367    "pub", "ref", "return", "self", "Self", "static", "struct", "super", "trait", "true", "type",
368    "unsafe", "use", "where", "while", "abstract", "become", "box", "do", "final", "macro",
369    "override", "priv", "try", "typeof", "unsized", "virtual", "yield",
370];
371
372fn rust_ident(name: &str) -> String {
373    let ident = snake(name);
374    if RUST_KEYWORDS.contains(&ident.as_str()) {
375        format!("{ident}_")
376    } else {
377        ident
378    }
379}
380
381fn rust_type(kind: Kind) -> &'static str {
382    match kind {
383        Kind::Str => "String",
384        Kind::Int => "i64",
385        Kind::Num => "f64",
386        Kind::Bool => "bool",
387        Kind::List => "Vec<Value>",
388        Kind::Object | Kind::Any => "Value",
389    }
390}
391
392fn rust_project(
393    spec: &SessionSpec,
394    tools: &[ProjectTool],
395    options: &ProjectOptions,
396) -> Vec<ProjectFile> {
397    vec![
398        ProjectFile::new("Cargo.toml", rust_cargo_toml(spec, options)),
399        ProjectFile::new("agent.json", spec_bound_to(spec, None)),
400        ProjectFile::new("src/main.rs", rust_main(spec)),
401        ProjectFile::new("src/tools.rs", rust_tools(tools)),
402        ProjectFile::new("README.md", readme(spec, ProjectLanguage::Rust, tools)),
403        ProjectFile::new(".gitignore", "/target\n".into()),
404    ]
405}
406
407fn rust_cargo_toml(spec: &SessionSpec, options: &ProjectOptions) -> String {
408    let mut features = vec!["gemini-llm"];
409    if spec.modality == SpecModality::Audio {
410        features.push("voice-io");
411    }
412    if spec.tools.iter().any(|t| t.http.is_some())
413        || spec
414            .skills
415            .iter()
416            .any(|skill| skill.tools.iter().any(|tool| tool.tool.http.is_some()))
417    {
418        features.push("http-tools");
419    }
420    if !spec.decisions.is_empty() {
421        features.push("ai-gateway");
422    }
423    let features = features
424        .iter()
425        .map(|f| quoted(f))
426        .collect::<Vec<_>>()
427        .join(", ");
428    let source = |krate: &str| match &options.sdk {
429        SdkSource::Registry => format!("version = \"{}\"", env!("CARGO_PKG_VERSION")),
430        SdkSource::Path(root) => format!(
431            "path = {}",
432            quoted(&format!("{}/crates/{krate}", root.trim_end_matches('/')))
433        ),
434    };
435    let mut out = format!(
436        "[package]\nname = \"{}\"\nversion = \"0.1.0\"\nedition = \"2024\"\npublish = false\n\n\
437         [dependencies]\ngemini-adk-fluent-rs = {{ {}, features = [{features}] }}\n",
438        project_name(spec),
439        source("gemini-adk-fluent-rs"),
440    );
441    if spec.requires_memory() {
442        let _ = writeln!(
443            out,
444            "gemini-memory-rs = {{ {} }}",
445            source("gemini-memory-rs")
446        );
447    }
448    out.push_str(
449        "serde = { version = \"1\", features = [\"derive\"] }\nserde_json = \"1\"\n\
450         tokio = { version = \"1\", features = [\"full\"] }\n\n\
451         # A project of its own, even when generated inside another workspace.\n[workspace]\n",
452    );
453    out
454}
455
456fn rust_main(spec: &SessionSpec) -> String {
457    let mut out = String::new();
458    let _ = writeln!(
459        out,
460        "//! {}: runs the agent in `agent.json`.",
461        display_name(spec)
462    );
463    out.push_str(
464        "//!\n//! `agent.json` is the agent: model, instruction, conversation, tool\n\
465         //! declarations and tests. `src/tools.rs` implements its tools.\n\n\
466         mod tools;\n\n",
467    );
468    let decides = !spec.decisions.is_empty();
469    // Extraction that names its model (`models.extraction`) is resolved by
470    // the spec; only unnamed extraction needs the environment's model.
471    let default_extraction = spec.requires_extraction() && spec.uses_default_extraction_model();
472    if !default_extraction && !spec.requires_memory() && !decides {
473        out.push_str("use gemini_adk_fluent_rs::prelude::*;\n");
474    } else {
475        out.push_str("use std::sync::Arc;\n\nuse gemini_adk_fluent_rs::prelude::*;\n");
476    }
477    out.push_str(
478        "use gemini_adk_fluent_rs::spec::SessionSpec;\n\n\
479         /// The agent, as data. Compiled in, so the binary is self-contained.\n\
480         const SPEC: &str = include_str!(\"../agent.json\");\n\n\
481         fn spec() -> Result<SessionSpec, String> {\n    \
482         SessionSpec::from_value(serde_json::from_str(SPEC).map_err(|e| e.to_string())?)\n}\n\n\
483         #[tokio::main]\n\
484         async fn main() -> Result<(), Box<dyn std::error::Error>> {\n    \
485         let spec = spec()?;\n    \
486         let state = State::new();\n",
487    );
488    let needs_more = default_extraction || spec.requires_memory() || decides;
489    if needs_more {
490        out.push_str("    let resources = gemini_adk_fluent_rs::spec::SpecResources {\n");
491        if default_extraction {
492            out.push_str(
493                "        // The out-of-band model behind `extract` entries that name no model\n        \
494                 // (GEMINI_TEXT_MODEL, or gemini-flash-latest). Prefer models.extraction.\n        \
495                 extraction_llm: Some(Arc::new(GeminiLlm::from_env()?)),\n",
496            );
497        }
498        if decides {
499            out.push_str(
500                "        // Jev on Vercel AI Gateway, answering the spec's `decisions`. Reads\n        \
501                 // AI_GATEWAY_API_KEY (for example from .env.local).\n        \
502                 decision_model: Some(Arc::new(\n            \
503                 gemini_adk_fluent_rs::gemini_adk_rs::decision::GatewayDecisionModel::from_env()?,\n        \
504                 )),\n",
505            );
506        }
507        if spec.requires_memory() {
508            out.push_str(
509                "        // An in-memory engine; swap in a durable store for production.\n        \
510                 memory: Some({\n            \
511                 use gemini_memory_rs::prelude::{MemoryEngine, SessionId, UserId};\n            \
512                 use gemini_memory_rs::runtime::SessionMemoryBinding;\n            \
513                 let engine = MemoryEngine::in_memory(UserId::new(\"user\"));\n            \
514                 let session = Arc::new(engine.begin_session(SessionId::new(\"session\")));\n            \
515                 Arc::new(SessionMemoryBinding::new(session))\n        \
516                 }),\n",
517            );
518        }
519        out.push_str("        ..tools::resources()\n    };\n");
520    } else {
521        out.push_str("    let resources = tools::resources();\n");
522    }
523    out.push_str("    let session = spec\n        .apply(Live::builder(), &state, &resources)?\n");
524    match spec.modality {
525        SpecModality::Text => {
526            out.push_str(
527                "        .on_text(|t| print!(\"{t}\"))\n        \
528                 .on_turn_complete(|| async { println!() })\n        \
529                 .connect_from_env()\n        .await?;\n\n    \
530                 // Type a line, read the reply.\n    \
531                 let stdin = std::io::stdin();\n    \
532                 let mut line = String::new();\n    \
533                 while stdin.read_line(&mut line)? > 0 {\n        \
534                 session.send_text(line.trim()).await?;\n        \
535                 line.clear();\n    }\n    \
536                 session.disconnect().await?;\n",
537            );
538        }
539        SpecModality::Audio => {
540            out.push_str(
541                "        .connect_from_env()\n        .await?;\n\n    \
542                 // Microphone in, speakers out, barge-in handled.\n    \
543                 session.talk().await?;\n",
544            );
545        }
546    }
547    out.push_str(
548        r#"    Ok(())
549}
550
551#[cfg(test)]
552mod tests {
553    use super::*;
554
555    /// The spec validates, and its embedded tests and scenarios pass.
556    #[tokio::test]
557    async fn the_spec_holds() {
558        let spec = spec().unwrap();
559        let validation = spec.validate();
560        assert!(validation.valid, "{:?}", validation.errors);
561        for report in spec.run_tests() {
562            assert!(report.passed, "test {}: {:?}", report.name, report.failures);
563        }
564        for report in spec.run_scenarios().await {
565            assert!(
566                report.passed,
567                "scenario {}: {:?}",
568                report.name, report.error
569            );
570        }
571    }
572
573    #[tokio::test]
574    async fn task_scenarios_hold() {
575        let spec = spec().unwrap();
576        for report in spec.run_task_scenarios().await {
577            assert!(
578                report.passed,
579                "task scenario {}: {:?}",
580                report.name, report.error
581            );
582        }
583    }
584
585    /// Every implementation belongs to a tool the spec declares.
586    #[test]
587    fn every_implementation_is_declared() {
588        let spec = spec().unwrap();
589        for name in tools::resources().tools.keys() {
590            assert!(
591                spec.tools.iter().any(|t| &t.name == name)
592                    || spec.skills.iter().any(|s| s
593                        .tools
594                        .iter()
595                        .any(|t| format!("{}/{}", s.name, t.tool.name) == *name)),
596                "{name} is not declared in agent.json"
597            );
598        }
599    }
600}
601"#,
602    );
603    out
604}
605
606fn rust_tools(tools: &[ProjectTool]) -> String {
607    let mut out = String::from(
608        "//! One function per tool `agent.json` declares as a mock.\n//!\n\
609         //! Each returns the spec's mock response until you replace its body. The\n\
610         //! declaration in `agent.json` stays what the model sees, and the spec's\n\
611         //! `set_state` and `save_response_as` still apply to what you return.\n\n",
612    );
613    if tools.is_empty() {
614        out.push_str(
615            "use gemini_adk_fluent_rs::spec::SpecResources;\n\n\
616             /// The implementations passed to `SessionSpec::apply`. The spec\n\
617             /// declares no mock tools, so there are none.\n\
618             pub fn resources() -> SpecResources {\n    SpecResources::default()\n}\n",
619        );
620        return out;
621    }
622    out.push_str(
623        "use std::future::Future;\n\n\
624         use gemini_adk_fluent_rs::prelude::*;\n\
625         use gemini_adk_fluent_rs::spec::SpecResources;\n\
626         use serde::Deserialize;\n\
627         use serde::de::DeserializeOwned;\n\
628         use serde_json::{Value, json};\n",
629    );
630    for tool in tools {
631        let args = format!("{}Args", tool.type_ident);
632        let fields = fields(tool);
633        let _ = writeln!(out, "\n/// Arguments of `{}`.", tool.name);
634        out.push_str("#[derive(Debug, Clone, Deserialize)]\n");
635        if !fields.is_empty() {
636            out.push_str("#[allow(dead_code, reason = \"read once the body is real\")]\n");
637        }
638        if fields.is_empty() {
639            let _ = writeln!(out, "pub struct {args} {{}}\n");
640        } else {
641            let _ = writeln!(out, "pub struct {args} {{");
642        }
643        for field in &fields {
644            if let Some(description) = &field.description {
645                let _ = writeln!(out, "    /// {}", one_line(description));
646            }
647            if !field.choices.is_empty() {
648                let _ = writeln!(out, "    /// One of: {}.", field.choices.join(", "));
649            }
650            let ident = rust_ident(&field.json);
651            if ident != field.json {
652                let _ = writeln!(out, "    #[serde(rename = {})]", quoted(&field.json));
653            }
654            let ty = rust_type(field.kind);
655            if field.required {
656                let _ = writeln!(out, "    pub {ident}: {ty},");
657            } else {
658                let _ = writeln!(out, "    #[serde(default)]\n    pub {ident}: Option<{ty}>,");
659            }
660        }
661        if !fields.is_empty() {
662            out.push_str("}\n\n");
663        }
664        if !tool.description.is_empty() {
665            let _ = writeln!(out, "/// {}", one_line(&tool.description));
666        }
667        let ident = rust_ident(&tool.ident);
668        let signature =
669            format!("pub async fn {ident}(args: {args}) -> Result<Value, ToolError> {{");
670        let signature = if signature.len() > 100 {
671            format!("pub async fn {ident}(\n    args: {args},\n) -> Result<Value, ToolError> {{")
672        } else {
673            signature
674        };
675        // Keep token width independent of Unicode display width. These are Rust
676        // string escapes inside json!, so the returned JSON values are unchanged.
677        let literal: String = mock_response(tool)
678            .to_string()
679            .chars()
680            .map(|character| {
681                if character.is_ascii() {
682                    character.to_string()
683                } else {
684                    character.escape_unicode().to_string()
685                }
686            })
687            .collect();
688        let response = format!("json!({literal})");
689        let returned = if response.len() + 8 <= 100 {
690            format!("Ok({response})")
691        } else {
692            format!("Ok(\n        {response},\n    )")
693        };
694        let _ = writeln!(
695            out,
696            "{signature}\n    \
697             let _ = args;\n    \
698             // The mock response from agent.json. Replace with the real call.\n    \
699             {returned}\n}}"
700        );
701    }
702    out.push_str(
703        "\n/// The implementations passed to `SessionSpec::apply`.\n\
704         pub fn resources() -> SpecResources {\n    ",
705    );
706    let calls: Vec<String> = tools
707        .iter()
708        .map(|t| {
709            let function = rust_ident(&t.ident);
710            match &t.skill {
711                Some(skill) => {
712                    let typed_args = format!("{}, {function}", quoted(&t.name));
713                    let typed = format!("typed({typed_args})");
714                    let arguments = format!("{}, {typed}", quoted(skill));
715                    if arguments.len() <= 60 {
716                        format!(".implement_skill({arguments})")
717                    } else {
718                        let typed = if typed_args.len() <= 60 {
719                            typed
720                        } else {
721                            format!("typed(\n                {},\n                {function},\n            )",quoted(&t.name))
722                        };
723                        format!(".implement_skill(\n            {},\n            {typed},\n        )",quoted(skill))
724                    }
725                },
726                None => format!(".implement(typed({}, {function}))", quoted(&t.name)),
727            }
728        })
729        .collect();
730    // rustfmt keeps a short chain on one line.
731    let chain = format!("SpecResources::default(){}", calls.concat());
732    if chain.len() <= 60 {
733        out.push_str(&chain);
734    } else {
735        out.push_str("SpecResources::default()");
736        for call in &calls {
737            let _ = write!(out, "\n        {call}");
738        }
739    }
740    out.push_str(
741        "\n}\n\n\
742         /// A tool that parses its arguments into `A` before calling `f`.\n\
743         fn typed<A, F, Fut>(name: &str, f: F) -> SimpleTool\n\
744         where\n    \
745         A: DeserializeOwned,\n    \
746         F: Fn(A) -> Fut + Send + Sync + 'static,\n    \
747         Fut: Future<Output = Result<Value, ToolError>> + Send + 'static,\n\
748         {\n    \
749         SimpleTool::new(name, \"\", None, move |args| {\n        \
750         let call = serde_json::from_value::<A>(args)\n            \
751         .map(&f)\n            \
752         .map_err(|e| ToolError::InvalidArgs(e.to_string()));\n        \
753         async move { call?.await }\n    })\n}\n",
754    );
755    out
756}
757
758// ── Python ──────────────────────────────────────────────────────────────────
759
760const PYTHON_KEYWORDS: &[&str] = &[
761    "False", "None", "True", "and", "as", "assert", "async", "await", "break", "class", "continue",
762    "def", "del", "elif", "else", "except", "finally", "for", "from", "global", "if", "import",
763    "in", "is", "lambda", "nonlocal", "not", "or", "pass", "raise", "return", "try", "while",
764    "with", "yield",
765];
766
767fn python_ident(name: &str) -> String {
768    let ident = snake(name);
769    if PYTHON_KEYWORDS.contains(&ident.as_str()) {
770        format!("{ident}_")
771    } else {
772        ident
773    }
774}
775
776fn python_type(field: &Field) -> String {
777    if !field.choices.is_empty() && field.kind == Kind::Str {
778        let choices: Vec<String> = field.choices.iter().map(|c| quoted(c)).collect();
779        return format!("Literal[{}]", choices.join(", "));
780    }
781    match field.kind {
782        Kind::Str => "str",
783        Kind::Int => "int",
784        Kind::Num => "float",
785        Kind::Bool => "bool",
786        Kind::List => "list[Any]",
787        Kind::Object => "dict[str, Any]",
788        Kind::Any => "Any",
789    }
790    .to_string()
791}
792
793/// A JSON value as a Python literal.
794fn python_literal(value: &Value) -> String {
795    match value {
796        Value::Null => "None".into(),
797        Value::Bool(true) => "True".into(),
798        Value::Bool(false) => "False".into(),
799        Value::Number(n) => n.to_string(),
800        Value::String(s) => quoted(s),
801        Value::Array(items) => format!(
802            "[{}]",
803            items
804                .iter()
805                .map(python_literal)
806                .collect::<Vec<_>>()
807                .join(", ")
808        ),
809        Value::Object(map) => format!(
810            "{{{}}}",
811            map.iter()
812                .map(|(k, v)| format!("{}: {}", quoted(k), python_literal(v)))
813                .collect::<Vec<_>>()
814                .join(", ")
815        ),
816    }
817}
818
819fn python_project(spec: &SessionSpec, tools: &[ProjectTool]) -> Vec<ProjectFile> {
820    let name = project_name(spec);
821    vec![
822        ProjectFile::new("agent.json", spec_bound_to(spec, Some(PYTHON_TOOL_SERVER))),
823        ProjectFile::new("tools.py", python_tools(spec, tools)),
824        ProjectFile::new("server.py", python_server(&name)),
825        ProjectFile::new("test_tools.py", python_test()),
826        ProjectFile::new(
827            "pyproject.toml",
828            format!(
829                "[project]\nname = \"{name}-tools\"\nversion = \"0.1.0\"\n\
830                 requires-python = \">=3.10\"\ndependencies = [\"mcp>=2.2,<3\"]\n\n\
831                 [build-system]\nrequires = [\"setuptools>=69\"]\n\
832                 build-backend = \"setuptools.build_meta\"\n\n\
833                 [tool.setuptools]\npy-modules = [\"tools\", \"server\"]\n"
834            ),
835        ),
836        ProjectFile::new("README.md", readme(spec, ProjectLanguage::Python, tools)),
837        ProjectFile::new(".gitignore", "__pycache__/\n.venv/\n*.egg-info/\n".into()),
838    ]
839}
840
841fn python_tools(spec: &SessionSpec, tools: &[ProjectTool]) -> String {
842    let mut body = String::new();
843    let mut renamed = Vec::new();
844    let mut uses_field = false;
845    for tool in tools {
846        let fields = fields(tool);
847        let mut params = Vec::new();
848        let mut names = Vec::new();
849        for field in &fields {
850            let ident = python_ident(&field.json);
851            let mut ty = python_type(field);
852            if ident != field.json {
853                uses_field = true;
854                names.push((field.json.clone(), ident.clone()));
855                ty = format!("Annotated[{ty}, Field(alias={})]", quoted(&field.json));
856            }
857            if field.required {
858                params.push(format!("{ident}: {ty}"));
859            } else {
860                params.push(format!("{ident}: {ty} | None = None"));
861            }
862        }
863        if !names.is_empty() {
864            renamed.push((
865                tool.skill.as_ref().map_or_else(
866                    || tool.name.clone(),
867                    |skill| format!("{skill}/{}", tool.name),
868                ),
869                names,
870            ));
871        }
872        let _ = write!(
873            body,
874            "\n\ndef {}({}) -> dict[str, Any]:\n",
875            python_ident(&tool.ident),
876            params.join(", ")
877        );
878        let mut doc = one_line(&tool.description);
879        if doc.is_empty() {
880            doc = format!("The `{}` tool.", tool.name);
881        }
882        let _ = writeln!(body, "    {}", python_docstring(&doc));
883        let response = mock_response(tool);
884        let response = if response.is_object() {
885            response
886        } else {
887            serde_json::json!({ "output": response })
888        };
889        let _ = writeln!(
890            body,
891            "    # The mock response from agent.json. Replace with the real call.\n    \
892             return {}",
893            python_literal(&response)
894        );
895    }
896
897    let mut out = format!(
898        "\"\"\"Tools for {}: one function per tool agent.json declares as a mock.\n\n\
899         Each returns the spec's mock response until you replace its body. The\n\
900         declaration in agent.json stays what the model sees, and the spec's\n\
901         `set_state` and `save_response_as` still apply to what you return.\n\"\"\"\n\n",
902        display_name(spec)
903    );
904    let mut typing = vec!["Any"];
905    if uses_field {
906        typing.insert(0, "Annotated");
907    }
908    if tools.iter().any(|t| {
909        fields(t)
910            .iter()
911            .any(|f| !f.choices.is_empty() && f.kind == Kind::Str)
912    }) {
913        typing.push("Literal");
914    }
915    let _ = writeln!(out, "from typing import {}", typing.join(", "));
916    if uses_field {
917        out.push_str("\nfrom pydantic import Field\n");
918    }
919    out.push_str(&body);
920    out.push_str("\n\n# Served by server.py, by the name agent.json declares.\nTOOLS = {\n");
921    for tool in tools {
922        let _ = writeln!(
923            out,
924            "    {}: {},",
925            quoted(&tool.skill.as_ref().map_or_else(
926                || tool.name.clone(),
927                |skill| format!("{skill}/{}", tool.name)
928            )),
929            python_ident(&tool.ident)
930        );
931    }
932    out.push_str("}\n");
933    out.push_str(
934        "\n# Parameters whose names are not Python identifiers: the name the model\n\
935         # sends, and the parameter it arrives as.\nRENAMED: dict[str, dict[str, str]] = {",
936    );
937    if renamed.is_empty() {
938        out.push_str("}\n");
939    } else {
940        out.push('\n');
941        for (tool, names) in renamed {
942            let pairs: Vec<String> = names
943                .iter()
944                .map(|(json, ident)| format!("{}: {}", quoted(json), quoted(ident)))
945                .collect();
946            let _ = writeln!(out, "    {}: {{{}}},", quoted(&tool), pairs.join(", "));
947        }
948        out.push_str("}\n");
949    }
950    out
951}
952
953fn python_docstring(text: &str) -> String {
954    format!(
955        "\"\"\"{}\"\"\"",
956        text.replace('\\', "\\\\").replace("\"\"\"", "\\\"\\\"\\\"")
957    )
958}
959
960fn python_server(name: &str) -> String {
961    format!(
962        "\"\"\"The MCP server agent.json points its tools at (stdio).\n\n\
963         Run by the runtime as `{PYTHON_TOOL_SERVER}`. You don't need to edit this file.\n\"\"\"\n\n\
964         import argparse\n\
965         import functools\n\n\
966         from mcp.server.mcpserver import MCPServer\n\n\
967         import tools\n\n\
968         def _renamed(fn, names):\n    \
969         \"\"\"Call `fn` with the parameters `names` maps, under their Python names.\"\"\"\n\n    \
970         @functools.wraps(fn)\n    \
971         def call(**kwargs):\n        \
972         return fn(**{{names.get(k, k): v for k, v in kwargs.items()}})\n\n    \
973         return call\n\n\n\
974         def build_server(skill=None):\n    \
975         server = MCPServer({})\n    \
976         for qualified, fn in tools.TOOLS.items():\n        \
977         owner, separator, local = qualified.partition(\"/\")\n        \
978         if (owner if separator else None) != skill:\n            continue\n        \
979         names = tools.RENAMED.get(qualified)\n        \
980         server.add_tool(_renamed(fn, names) if names else fn, name=local if separator else owner)\n    \
981         return server\n\n\
982         server = build_server()\n\n\
983         if __name__ == \"__main__\":\n    \
984         parser = argparse.ArgumentParser()\n    \
985         parser.add_argument(\"--skill\")\n    \
986         build_server(parser.parse_args().skill).run()\n",
987        quoted(&format!("{name}-tools"))
988    )
989}
990
991fn python_test() -> String {
992    format!(
993        "\"\"\"The server serves exactly the tools agent.json binds to it.\"\"\"\n\n\
994         import asyncio\n\
995         import json\n\
996         import pathlib\n\
997         import unittest\n\n\
998         import server\n\n\
999         SPEC = json.loads((pathlib.Path(__file__).parent / \"agent.json\").read_text())\n\n\n\
1000         class ServerMatchesSpec(unittest.TestCase):\n    \
1001         def test_serves_every_tool_bound_to_it(self):\n        \
1002         bound = {{t[\"name\"] for t in SPEC.get(\"tools\", []) if t.get(\"mcp\") == {}}}\n        \
1003         served = {{t.name for t in asyncio.run(server.server.list_tools())}}\n        \
1004         self.assertEqual(served, bound)\n        \
1005         for skill in SPEC.get(\"skills\", []):\n            \
1006         command = {} + \" --skill \" + skill[\"name\"]\n            \
1007         bound = {{t[\"name\"] for t in skill.get(\"tools\", []) if t.get(\"mcp\") == command}}\n            \
1008         served = {{t.name for t in asyncio.run(server.build_server(skill[\"name\"]).list_tools())}}\n            \
1009         self.assertEqual(served, bound)\n\n\n\
1010         if __name__ == \"__main__\":\n    unittest.main()\n",
1011        quoted(PYTHON_TOOL_SERVER),
1012        quoted(PYTHON_TOOL_SERVER)
1013    )
1014}
1015
1016// ── Go ──────────────────────────────────────────────────────────────────────
1017
1018fn go_type(kind: Kind) -> &'static str {
1019    match kind {
1020        Kind::Str => "string",
1021        Kind::Int => "int64",
1022        Kind::Num => "float64",
1023        Kind::Bool => "bool",
1024        Kind::List => "[]any",
1025        Kind::Object => "map[string]any",
1026        Kind::Any => "any",
1027    }
1028}
1029
1030/// A JSON value as a Go literal of type `any`.
1031fn go_literal(value: &Value) -> String {
1032    match value {
1033        Value::Null => "nil".into(),
1034        Value::Bool(b) => b.to_string(),
1035        Value::Number(n) => n.to_string(),
1036        Value::String(s) => quoted(s),
1037        Value::Array(items) => format!(
1038            "[]any{{{}}}",
1039            items.iter().map(go_literal).collect::<Vec<_>>().join(", ")
1040        ),
1041        Value::Object(map) => format!(
1042            "map[string]any{{{}}}",
1043            map.iter()
1044                .map(|(k, v)| format!("{}: {}", quoted(k), go_literal(v)))
1045                .collect::<Vec<_>>()
1046                .join(", ")
1047        ),
1048    }
1049}
1050
1051fn go_project(spec: &SessionSpec, tools: &[ProjectTool]) -> Vec<ProjectFile> {
1052    let name = project_name(spec);
1053    vec![
1054        ProjectFile::new("agent.json", spec_bound_to(spec, Some(GO_TOOL_SERVER))),
1055        ProjectFile::new(
1056            "go.mod",
1057            format!(
1058                "module {name}-tools\n\ngo 1.25\n\n\
1059                 require github.com/modelcontextprotocol/go-sdk {GO_MCP_SDK}\n"
1060            ),
1061        ),
1062        ProjectFile::new("tools.go", go_tools(spec, tools)),
1063        ProjectFile::new("main.go", go_main(&name, tools)),
1064        ProjectFile::new("main_test.go", go_test()),
1065        ProjectFile::new("README.md", readme(spec, ProjectLanguage::Go, tools)),
1066        ProjectFile::new(".gitignore", format!("/{name}-tools\n")),
1067    ]
1068}
1069
1070/// One struct field of a Go arguments type.
1071struct GoField {
1072    comments: Vec<String>,
1073    name: String,
1074    ty: &'static str,
1075    tag: String,
1076}
1077
1078fn go_tools(spec: &SessionSpec, tools: &[ProjectTool]) -> String {
1079    let mut out = format!(
1080        "// Tools for {}: one function per tool agent.json declares as a mock.\n//\n\
1081         // Each returns the spec's mock response until you replace its body. The\n\
1082         // declaration in agent.json stays what the model sees, and the spec's\n\
1083         // set_state and save_response_as still apply to what you return.\n\
1084         package main\n",
1085        display_name(spec)
1086    );
1087    if tools.is_empty() {
1088        return out;
1089    }
1090    out.push_str("\nimport \"context\"\n");
1091    for tool in tools {
1092        let fn_name = tool.type_ident.clone();
1093        let _ = write!(
1094            out,
1095            "\n// {fn_name}Args are the arguments of {}.\ntype {fn_name}Args struct {{\n",
1096            tool.name
1097        );
1098        // As gofmt lays it out: names and types aligned within each run of
1099        // fields that no comment line interrupts.
1100        let mut runs: Vec<Vec<GoField>> = Vec::new();
1101        for field in fields(tool) {
1102            let mut comments = Vec::new();
1103            if let Some(description) = &field.description {
1104                comments.push(one_line(description));
1105            }
1106            if !field.choices.is_empty() {
1107                comments.push(format!("One of: {}.", field.choices.join(", ")));
1108            }
1109            let omit = if field.required { "" } else { ",omitempty" };
1110            let tag = format!("`json:{}`", quoted(&format!("{}{omit}", field.json)));
1111            if !comments.is_empty() || runs.is_empty() {
1112                runs.push(Vec::new());
1113            }
1114            if let Some(run) = runs.last_mut() {
1115                run.push(GoField {
1116                    comments,
1117                    name: pascal(&field.json),
1118                    ty: go_type(field.kind),
1119                    tag,
1120                });
1121            }
1122        }
1123        for run in &runs {
1124            let name_width = run.iter().map(|f| f.name.len()).max().unwrap_or(0);
1125            let type_width = run.iter().map(|f| f.ty.len()).max().unwrap_or(0);
1126            for GoField {
1127                comments,
1128                name,
1129                ty,
1130                tag,
1131            } in run
1132            {
1133                for comment in comments {
1134                    let _ = writeln!(out, "\t// {comment}");
1135                }
1136                let _ = writeln!(out, "\t{name:name_width$} {ty:type_width$} {tag}");
1137            }
1138        }
1139        out.push_str("}\n\n");
1140        let description = one_line(&tool.description);
1141        if description.is_empty() {
1142            let _ = writeln!(out, "// {fn_name} implements the {} tool.", tool.name);
1143        } else {
1144            let _ = writeln!(out, "// {fn_name}: {description}");
1145        }
1146        let response = mock_response(tool);
1147        let response = if response.is_object() {
1148            response
1149        } else {
1150            serde_json::json!({ "output": response })
1151        };
1152        let _ = writeln!(
1153            out,
1154            "func {fn_name}(ctx context.Context, args {fn_name}Args) (map[string]any, error) {{\n\t\
1155             // The mock response from agent.json. Replace with the real call.\n\t\
1156             return {}, nil\n}}",
1157            go_literal(&response)
1158        );
1159    }
1160    out
1161}
1162
1163fn go_main(name: &str, tools: &[ProjectTool]) -> String {
1164    let mut out = format!(
1165        "// The MCP server agent.json points its tools at (stdio). Run by the\n\
1166         // runtime as `{GO_TOOL_SERVER}`. You don't need to edit this file.\n\
1167         package main\n\n\
1168         import (\n\t\"context\"\n\t\"flag\"\n\t\"log\"\n\n\t\"github.com/modelcontextprotocol/go-sdk/mcp\"\n)\n\n\
1169         func main() {{\n\t\
1170         skill := flag.String(\"skill\", \"\", \"Skill scope\")\n\tflag.Parse()\n\t\
1171         if err := newServer(*skill).Run(context.Background(), &mcp.StdioTransport{{}}); err != nil {{\n\t\t\
1172         log.Fatal(err)\n\t}}\n}}\n\n\
1173         // newServer serves each tool by the name agent.json declares.\n\
1174         func newServer(scopes ...string) *mcp.Server {{\n\t\
1175         scope := \"\"\n\tif len(scopes) > 0 {{\n\t\tscope = scopes[0]\n\t}}\n\t\
1176         _ = scope\n\t\
1177         server := mcp.NewServer(&mcp.Implementation{{Name: {}, Version: \"v0.1.0\"}}, nil)\n",
1178        quoted(&format!("{name}-tools"))
1179    );
1180    for tool in tools {
1181        let _ = writeln!(
1182            out,
1183            "\tif scope == {} {{\n\t\tmcp.AddTool(server, &mcp.Tool{{Name: {}}}, serve({}))\n\t}}",
1184            quoted(tool.skill.as_deref().unwrap_or("")),
1185            quoted(&tool.name),
1186            tool.type_ident
1187        );
1188    }
1189    out.push_str(
1190        "\treturn server\n}\n\n\
1191         // serve adapts a tool function to MCP; its result is the structured content.\n\
1192         func serve[In any](fn func(context.Context, In) (map[string]any, error)) mcp.ToolHandlerFor[In, map[string]any] {\n\t\
1193         return func(ctx context.Context, _ *mcp.CallToolRequest, in In) (*mcp.CallToolResult, map[string]any, error) {\n\t\t\
1194         out, err := fn(ctx, in)\n\t\t\
1195         return nil, out, err\n\t}\n}\n",
1196    );
1197    out
1198}
1199
1200fn go_test() -> String {
1201    r#"package main
1202
1203import (
1204	"context"
1205	"encoding/json"
1206	"os"
1207	"sort"
1208	"testing"
1209
1210	"github.com/modelcontextprotocol/go-sdk/mcp"
1211)
1212
1213// Each server scope serves exactly the tools agent.json binds to it.
1214func TestServesEveryToolBoundToIt(t *testing.T) {
1215	data, err := os.ReadFile("agent.json")
1216	if err != nil {
1217		t.Fatal(err)
1218	}
1219	type tool struct {
1220		Name string `json:"name"`
1221		MCP  string `json:"mcp"`
1222	}
1223	var spec struct {
1224		Tools  []tool `json:"tools"`
1225		Skills []struct {
1226			Name  string `json:"name"`
1227			Tools []tool `json:"tools"`
1228		} `json:"skills"`
1229	}
1230	if err := json.Unmarshal(data, &spec); err != nil {
1231		t.Fatal(err)
1232	}
1233	scopes := map[string][]tool{"": spec.Tools}
1234	for _, skill := range spec.Skills {
1235		scopes[skill.Name] = skill.Tools
1236	}
1237	for scope, tools := range scopes {
1238		t.Run(scope, func(t *testing.T) {
1239			command := __SERVER__
1240			if scope != "" {
1241				command += " --skill " + scope
1242			}
1243			var bound []string
1244			for _, tool := range tools {
1245				if tool.MCP == command {
1246					bound = append(bound, tool.Name)
1247				}
1248			}
1249			ctx := context.Background()
1250			clientTransport, serverTransport := mcp.NewInMemoryTransports()
1251			if _, err := newServer(scope).Connect(ctx, serverTransport, nil); err != nil {
1252				t.Fatal(err)
1253			}
1254			client := mcp.NewClient(&mcp.Implementation{Name: "test", Version: "v0.0.0"}, nil)
1255			session, err := client.Connect(ctx, clientTransport, nil)
1256			if err != nil {
1257				t.Fatal(err)
1258			}
1259			defer session.Close()
1260			listed, err := session.ListTools(ctx, nil)
1261			if err != nil {
1262				t.Fatal(err)
1263			}
1264			var served []string
1265			for _, tool := range listed.Tools {
1266				served = append(served, tool.Name)
1267			}
1268			sort.Strings(bound)
1269			sort.Strings(served)
1270			if len(bound) != len(served) {
1271				t.Fatalf("agent.json binds %v, server serves %v", bound, served)
1272			}
1273			for i := range bound {
1274				if bound[i] != served[i] {
1275					t.Fatalf("agent.json binds %v, server serves %v", bound, served)
1276				}
1277			}
1278		})
1279	}
1280}
1281"#
1282    .replace("__SERVER__", &quoted(GO_TOOL_SERVER))
1283}
1284
1285// ── README ──────────────────────────────────────────────────────────────────
1286
1287fn display_name(spec: &SessionSpec) -> String {
1288    if spec.name.is_empty() {
1289        "agent".into()
1290    } else {
1291        one_line(&spec.name)
1292    }
1293}
1294
1295fn readme(spec: &SessionSpec, language: ProjectLanguage, tools: &[ProjectTool]) -> String {
1296    let mut out = format!("# {}\n\n", display_name(spec));
1297    if !spec.description.is_empty() {
1298        let _ = writeln!(out, "{}\n", one_line(&spec.description));
1299    }
1300    out.push_str(
1301        "`agent.json` is the agent: model, instruction, conversation, tool\n\
1302         declarations and tests. Edit it in Flow Studio or by hand.\n\n",
1303    );
1304    let file = match language {
1305        ProjectLanguage::Rust => "`src/tools.rs`",
1306        ProjectLanguage::Python => "`tools.py`",
1307        ProjectLanguage::Go => "`tools.go`",
1308    };
1309    if tools.is_empty() {
1310        out.push_str("The spec declares no mock tools, so there is nothing to implement.\n\n");
1311    } else {
1312        let names: Vec<String> = tools
1313            .iter()
1314            .map(|t| match &t.skill {
1315                Some(skill) => format!("`{skill}/{}`", t.name),
1316                None => format!("`{}`", t.name),
1317            })
1318            .collect();
1319        let _ = writeln!(
1320            out,
1321            "{file} has one function per tool the spec declares as a mock ({}). Each\n\
1322             returns the spec's mock response until you replace its body. What the\n\
1323             model sees stays the declaration in `agent.json`, and the spec's\n\
1324             `set_state` and `save_response_as` still apply to what you return.\n",
1325            names.join(", ")
1326        );
1327    }
1328    if tools.iter().any(|tool| tool.skill.is_some()) {
1329        out.push_str("Skill tools keep local names in `agent.json`. Generated functions include the skill scope; Rust binds them with `implement_skill`, and Python/Go bindings select the scope with `--skill`. Replace each scoped function independently. Commit argument types include the required idempotency key.\n\n");
1330    }
1331    match language {
1332        ProjectLanguage::Rust => out.push_str(
1333            "```bash\ncargo test   # the spec validates; its tests and scenarios pass\n\
1334             cargo run    # a live session (GEMINI_API_KEY, or Vertex AI settings)\n```\n",
1335        ),
1336        ProjectLanguage::Python => {
1337            let _ = write!(
1338                out,
1339                "The tools run as an MCP server: `agent.json` binds each of them to\n\
1340                 `{PYTHON_TOOL_SERVER}`, which a runtime starts from this directory.\n\n\
1341                 ```bash\npython3 -m venv .venv && . .venv/bin/activate\npip install -e .\n\
1342                 python -m unittest              # the server serves each declared scope\n"
1343            );
1344        }
1345        ProjectLanguage::Go => {
1346            let _ = write!(
1347                out,
1348                "The tools run as an MCP server: `agent.json` binds each of them to\n\
1349                 `{GO_TOOL_SERVER}`, which a runtime starts from this directory. For\n\
1350                 production, build a binary and point the bindings at it.\n\n\
1351                 ```bash\ngo mod tidy\n\
1352                 go test ./...                   # the server serves each declared scope\n"
1353            );
1354        }
1355    }
1356    if language != ProjectLanguage::Rust {
1357        out.push_str("adk spec test agent.json        # governed tests and task scenarios\n");
1358        if spec.skills.is_empty() {
1359            out.push_str("adk spec call agent.json <tool> '{\"arg\": 1}'   # one root tool call through the server\n");
1360        }
1361        if spec.requires_memory() {
1362            out.push_str("adk spec codegen agent.json --lang rust --out host\ncargo run --manifest-path host/Cargo.toml\n```\n\n");
1363            out.push_str("Run the Rust host from this tools-project directory so the existing MCP commands resolve here. The host configures the declared memory engine and preserves these MCP bindings. For an unreleased local SDK checkout, add `--sdk-path /path/to/gemini-rs` to `adk spec codegen`. Live sessions need `GEMINI_API_KEY` or Vertex AI settings.\n");
1364        } else {
1365            out.push_str("adk spec run agent.json         # a live session\n```\n");
1366        }
1367        if !spec.skills.is_empty() {
1368            out.push_str("\nOpen `agent.json` in Flow Studio and use Tasks to start a skill, inspect admission, propose an operation, and approve or decline its exact arguments. `adk spec test` runs the controlled scenarios offline; direct `adk spec call` addresses root tools and is not a task-admission path.\n");
1369        }
1370    }
1371    out
1372}
1373
1374#[cfg(test)]
1375mod tests {
1376    use super::*;
1377    use serde_json::json;
1378
1379    fn spec() -> SessionSpec {
1380        SessionSpec::from_value(json!({
1381            "name": "Table Booking",
1382            "description": "Books tables.",
1383            "tools": [
1384                {
1385                    "name": "book_table",
1386                    "description": "Book a table.",
1387                    "parameters": {
1388                        "type": "object",
1389                        "properties": {
1390                            "party_size": { "type": "integer", "description": "Guests." },
1391                            "from": { "type": "string" },
1392                            "seating": { "type": "string", "enum": ["inside", "terrace"] },
1393                            "notes": { "type": ["string", "null"] },
1394                            "type": { "type": "string" }
1395                        },
1396                        "required": ["party_size", "from"]
1397                    },
1398                    "response": { "confirmation": "MOCK-1", "held": true },
1399                    "set_state": { "booked": true }
1400                },
1401                { "name": "lookup", "http": { "url": "https://api.example.com/x" } },
1402                { "name": "ping", "response": "pong" }
1403            ],
1404            "flow": { "steps": [{ "id": "s", "allow": ["book_table", "lookup", "ping"], "terminal": true }] }
1405        }))
1406        .unwrap()
1407    }
1408
1409    fn file<'a>(files: &'a [ProjectFile], path: &str) -> &'a str {
1410        &files
1411            .iter()
1412            .find(|f| f.path == path)
1413            .unwrap_or_else(|| panic!("{path} missing"))
1414            .contents
1415    }
1416
1417    #[test]
1418    fn a_rust_project_implements_the_mocks_in_process() {
1419        let files = spec().to_project(ProjectLanguage::Rust);
1420        let tools = file(&files, "src/tools.rs");
1421        assert!(tools.contains("pub struct BookTableArgs"));
1422        assert!(tools.contains("pub party_size: i64,"));
1423        assert!(tools.contains("pub from: String,"));
1424        assert!(tools.contains(
1425            "#[serde(rename = \"type\")]\n    #[serde(default)]\n    pub type_: Option<String>,"
1426        ));
1427        assert!(tools.contains("pub notes: Option<String>,"));
1428        assert!(tools.contains(r#"Ok(json!({"confirmation":"MOCK-1","held":true}))"#));
1429        assert!(tools.contains(".implement(typed(\"ping\", ping))"));
1430        // A tool with its own binding keeps it.
1431        assert!(!tools.contains("lookup"));
1432        let cargo = file(&files, "Cargo.toml");
1433        assert!(cargo.contains(&format!("version = \"{}\"", env!("CARGO_PKG_VERSION"))));
1434        assert!(cargo.contains("\"http-tools\""));
1435        assert!(cargo.contains("name = \"table-booking\""));
1436
1437        let local = spec().to_project_with(
1438            ProjectLanguage::Rust,
1439            &ProjectOptions {
1440                sdk: SdkSource::Path("/src/gemini-rs/".into()),
1441            },
1442        );
1443        assert!(
1444            file(&local, "Cargo.toml")
1445                .contains("path = \"/src/gemini-rs/crates/gemini-adk-fluent-rs\"")
1446        );
1447        // agent.json is the spec unchanged.
1448        let agent: Value = serde_json::from_str(file(&files, "agent.json")).unwrap();
1449        assert!(agent["tools"][0].get("mcp").is_none());
1450    }
1451
1452    #[test]
1453    fn named_extraction_needs_no_environment_model() {
1454        let mut spec = spec();
1455        spec.extract.push(
1456            serde_json::from_value(json!({
1457                "name": "notes", "instruction": "Notes.", "schema": { "type": "object" }
1458            }))
1459            .unwrap(),
1460        );
1461        let unnamed = spec.to_project(ProjectLanguage::Rust);
1462        assert!(file(&unnamed, "src/main.rs").contains("extraction_llm: Some("));
1463
1464        spec.models.extraction = Some("gemini-3.1-flash-lite".into());
1465        let named = spec.to_project(ProjectLanguage::Rust);
1466        let main = file(&named, "src/main.rs");
1467        assert!(!main.contains("extraction_llm"), "{main}");
1468        assert!(
1469            !main.contains("use std::sync::Arc;"),
1470            "unused import: {main}"
1471        );
1472    }
1473
1474    #[test]
1475    fn a_python_project_serves_the_mocks_over_mcp() {
1476        let files = spec().to_project(ProjectLanguage::Python);
1477        let tools = file(&files, "tools.py");
1478        assert!(tools.contains(
1479            "def book_table(from_: Annotated[str, Field(alias=\"from\")], party_size: int, \
1480             notes: str | None = None, seating: Literal[\"inside\", \"terrace\"] | None = None, \
1481             type: str | None = None) -> dict[str, Any]:"
1482        ));
1483        assert!(tools.contains("return {\"confirmation\": \"MOCK-1\", \"held\": True}"));
1484        assert!(tools.contains("return {\"output\": \"pong\"}"));
1485        assert!(tools.contains("\"book_table\": {\"from\": \"from_\"},"));
1486        let agent: Value = serde_json::from_str(file(&files, "agent.json")).unwrap();
1487        assert_eq!(agent["tools"][0]["mcp"], PYTHON_TOOL_SERVER);
1488        assert!(
1489            agent["tools"][1].get("mcp").is_none(),
1490            "an HTTP tool keeps its binding"
1491        );
1492        // The bound spec still validates and keeps its mock for offline tests.
1493        let bound = SessionSpec::from_value(agent).unwrap();
1494        let validation = bound.validate();
1495        assert!(
1496            validation.errors.iter().all(|e| e.contains("http-tools")),
1497            "{:?}",
1498            validation.errors
1499        );
1500        assert!(bound.tools[0].response.is_some());
1501    }
1502
1503    #[test]
1504    fn a_go_project_serves_the_mocks_over_mcp() {
1505        let files = spec().to_project(ProjectLanguage::Go);
1506        let tools = file(&files, "tools.go");
1507        // Aligned as gofmt aligns them: per run of fields between comments.
1508        assert!(tools.contains(
1509            "\t// Guests.\n\tPartySize int64  `json:\"party_size\"`\n\tNotes     string `json:\"notes,omitempty\"`\n"
1510        ));
1511        assert!(
1512            tools.contains(
1513                "return map[string]any{\"confirmation\": \"MOCK-1\", \"held\": true}, nil"
1514            )
1515        );
1516        let main = file(&files, "main.go");
1517        assert!(
1518            main.contains("mcp.AddTool(server, &mcp.Tool{Name: \"book_table\"}, serve(BookTable))")
1519        );
1520        let agent: Value = serde_json::from_str(file(&files, "agent.json")).unwrap();
1521        assert_eq!(agent["tools"][2]["mcp"], GO_TOOL_SERVER);
1522    }
1523
1524    #[test]
1525    fn names_become_identifiers() {
1526        assert_eq!(snake("bookTable"), "book_table");
1527        assert_eq!(snake("book-table"), "book_table");
1528        assert_eq!(snake("book--__table"), "book_table");
1529        assert_eq!(pascal("book_table"), "BookTable");
1530        assert_eq!(pascal("2fa"), "T2fa");
1531        assert_eq!(rust_ident("type"), "type_");
1532        assert_eq!(python_ident("class"), "class_");
1533        assert_eq!(project_name(&SessionSpec::default()), "agent");
1534        assert_eq!("PY".parse::<ProjectLanguage>(), Ok(ProjectLanguage::Python));
1535    }
1536    fn scoped_skills() -> SessionSpec {
1537        SessionSpec::from_value(json!({"name":"support","skills":[
1538            {"name":"billing","version":"2","tools":[
1539                {"name":"lookup","effect":{"kind":"read"},"parameters":{"type":"object","properties":{"account":{"type":"string"}},"required":["account"]},"response":{"balance":75}},
1540                {"name":"pay","effect":{"kind":"commit","idempotency_argument":"request_id"},"response":{"receipt":"paid"}},
1541                {"name":"remote","effect":{"kind":"read"},"mcp":"original-server"}
1542            ]},
1543            {"name":"faq","version":"7","tools":[
1544                {"name":"lookup","effect":{"kind":"read"},"response":{"answer":"hours"}}
1545            ]}
1546        ]})).expect("skill spec")
1547    }
1548
1549    #[test]
1550    fn rust_skill_projects_use_scoped_bindings_and_typed_commit_arguments() {
1551        let spec = scoped_skills();
1552        assert!(spec.validate().valid);
1553        let files = spec.to_project(ProjectLanguage::Rust);
1554        let tools = file(&files, "src/tools.rs");
1555        assert!(tools.contains("pub async fn billing_lookup(args: BillingLookupArgs)"));
1556        assert!(tools.contains("pub async fn faq_lookup(args: FaqLookupArgs)"));
1557        assert!(tools.contains(".implement_skill(\"billing\", typed(\"lookup\", billing_lookup))"));
1558        assert!(tools.contains(".implement_skill(\"faq\", typed(\"lookup\", faq_lookup))"));
1559        assert!(tools.contains("pub request_id: String,"));
1560        assert!(tools.contains("Ok(json!({\"balance\":75}))"));
1561        assert!(tools.contains("Ok(json!({\"answer\":\"hours\"}))"));
1562        assert!(
1563            !tools.contains("billing_remote"),
1564            "existing bindings are preserved"
1565        );
1566        let unchanged: Value = serde_json::from_str(file(&files, "agent.json")).expect("spec");
1567        assert_eq!(unchanged, serde_json::to_value(spec).expect("spec"));
1568        assert!(file(&files, "src/main.rs").contains("spec.skills.iter().any"));
1569    }
1570
1571    #[test]
1572    fn mcp_skill_exports_bind_local_names_to_separate_server_scopes() {
1573        for (language, server, tools_file, main_file) in [
1574            (
1575                ProjectLanguage::Python,
1576                PYTHON_TOOL_SERVER,
1577                "tools.py",
1578                "server.py",
1579            ),
1580            (ProjectLanguage::Go, GO_TOOL_SERVER, "tools.go", "main.go"),
1581        ] {
1582            let files = scoped_skills().to_project(language);
1583            let value: Value = serde_json::from_str(file(&files, "agent.json")).expect("spec");
1584            assert_eq!(value["skills"][0]["tools"][0]["name"], "lookup");
1585            assert_eq!(
1586                value["skills"][0]["tools"][0]["mcp"],
1587                format!("{server} --skill billing")
1588            );
1589            assert_eq!(
1590                value["skills"][1]["tools"][0]["mcp"],
1591                format!("{server} --skill faq")
1592            );
1593            assert_eq!(value["skills"][0]["tools"][2]["mcp"], "original-server");
1594            let bound = SessionSpec::from_value(value).expect("bound spec");
1595            assert!(bound.validate().valid, "{:?}", bound.validate().errors);
1596            let tools = file(&files, tools_file);
1597            let main = file(&files, main_file);
1598            match language {
1599                ProjectLanguage::Python => {
1600                    assert!(tools.contains("\"billing/lookup\": billing_lookup"));
1601                    assert!(tools.contains("\"faq/lookup\": faq_lookup"));
1602                    assert!(tools.contains("def billing_pay(request_id: str)"));
1603                    assert!(main.contains("def build_server(skill=None):"));
1604                    assert!(
1605                        file(&files, "test_tools.py")
1606                            .contains("for skill in SPEC.get(\"skills\", [])")
1607                    );
1608                }
1609                ProjectLanguage::Go => {
1610                    assert!(tools.contains("RequestId string"));
1611                    assert!(main.contains("if scope == \"billing\" {\n\t\tmcp.AddTool(server, &mcp.Tool{Name: \"lookup\"}, serve(BillingLookup))\n\t}"));
1612                    assert!(main.contains("if scope == \"faq\" {\n\t\tmcp.AddTool(server, &mcp.Tool{Name: \"lookup\"}, serve(FaqLookup))\n\t}"));
1613                    assert!(
1614                        file(&files, "main_test.go").contains("scopes[skill.Name] = skill.Tools")
1615                    );
1616                }
1617                ProjectLanguage::Rust => unreachable!(),
1618            }
1619        }
1620    }
1621
1622    #[test]
1623    fn generated_identifiers_do_not_collide_after_scope_normalization() {
1624        let mut spec = scoped_skills();
1625        spec.skills[0].name = "Faq".into();
1626        let tools = stubbed_tools(&spec);
1627        assert_eq!(
1628            tools
1629                .iter()
1630                .map(|tool| &tool.ident)
1631                .collect::<std::collections::BTreeSet<_>>()
1632                .len(),
1633            tools.len()
1634        );
1635        assert_eq!(
1636            tools
1637                .iter()
1638                .map(|tool| &tool.type_ident)
1639                .collect::<std::collections::BTreeSet<_>>()
1640                .len(),
1641            tools.len()
1642        );
1643        let source = rust_tools(&tools);
1644        assert!(source.contains(".implement_skill(\"Faq\", typed(\"lookup\", faq_lookup))"));
1645        assert!(source.contains(".implement_skill(\"faq\", typed(\"lookup\", faq_lookup_2))"));
1646    }
1647    #[test]
1648    fn long_mock_responses_wrap_the_result_without_changing_json() {
1649        let mut spec = scoped_skills();
1650        let response = json!({"answer":"A controlled answer with enough text to cross the generated Rust line width and require wrapping the Result constructor."});
1651        spec.skills[0].tools[0].tool.response = Some(response.clone());
1652        let files = spec.to_project(ProjectLanguage::Rust);
1653        assert!(
1654            file(&files, "src/tools.rs")
1655                .contains(&format!("    Ok(\n        json!({response}),\n    )"))
1656        );
1657    }
1658    #[test]
1659    fn catalog_readmes_use_task_admission_and_memory_projects_use_a_rust_host() {
1660        for language in [ProjectLanguage::Python, ProjectLanguage::Go] {
1661            let mut spec = scoped_skills();
1662            let project = spec.to_project(language);
1663            let readme = file(&project, "README.md");
1664            assert!(readme.contains("adk spec test agent.json"));
1665            assert!(readme.contains("Flow Studio and use Tasks"));
1666            assert!(!readme.contains("adk spec call agent.json <tool>"));
1667            assert!(readme.contains("adk spec run agent.json"));
1668            spec.skills[0].memory = Some(super::super::MemorySpec::default());
1669            let project = spec.to_project(language);
1670            let readme = file(&project, "README.md");
1671            assert!(!readme.contains("adk spec run agent.json"));
1672            assert!(readme.contains("adk spec codegen agent.json --lang rust --out host"));
1673            assert!(readme.contains("cargo run --manifest-path host/Cargo.toml"));
1674            assert!(readme.contains("--sdk-path /path/to/gemini-rs"));
1675            assert!(readme.contains("preserves these MCP bindings"));
1676            assert!(readme.contains("from this tools-project directory"));
1677        }
1678    }
1679}
gemini_adk_fluent_rs/spec/project.rs

gemini_adk_fluent_rs/spec/
project.rs
