Foundations

The mental model. Read this tier once, top to bottom, and every other builder method in the library will slot into place.

        flowchart LR
    A[Architecture<br/>& concepts] --> B[Builders]
    B --> C[Expression<br/>language]
    B --> D[Data flow]
    C -.alternative syntax.-> B
    D -.which method<br/>does what.-> B

    classDef core fill:#e3f2fd,stroke:#1565c0,stroke-width:2px,color:#0d47a1
    class A,B,C,D core
    

Read in order

	Chapter	The one thing it teaches
1	Architecture & concepts	ADK has three channels — conversation, state, instruction — and every builder method touches exactly one of them.
2	Builders	Agent, Pipeline, FanOut, Loop. .build() returns a real LlmAgent — not a wrapper.
3	Expression language	>>, |, *, //, @ — immutable sub-expressions that compose without builders.
4	Data flow	Five orthogonal concerns: context, input, output, storage, contract. One method per concern. Confusion disappears.

After this tier you can ship any linear or parallel workflow. Pick the next tier when — and only when — you hit a concrete need it solves.