Type Alias AsyncSourceFn 

pub type AsyncSourceFn<In = State> = Arc<dyn Fn(In) -> Pin<Box<dyn Future<Output = Result<Value, String>> + Send>> + Send + Sync>;

An async source of a JSON value — the seam for a tool call, an HTTP fetch, an MCP request, or a workflow function node. In is what the source is bound from: the whole State by default, or a pre-bound args Value for extraction-kit field resolvers.

The Err(String) payload is a human-readable reason; it lands in {name}:error state keys and in extraction diagnostics.

Aliased Type

pub struct AsyncSourceFn<In = State> { /* private fields */ }