declare-parameter-producers

Declaring parameter producers with available_from

A command that takes an opaque handle — an id, uid, code, ticket number — cannot be called until something produces that handle. available_from records which command that is, turning a flat list of commands into a graph the planner can walk.

The hint

On the Input field, context-qualified:

class Signature:
    class Input(BaseModel):
        order_id: str = Field(
            description="The order to fetch",
            examples=["#W0000000"],
            json_schema_extra={'available_from': ['CustomerDesk/find_order']},
        )

The value is a list — name every command that can legitimately supply the handle.

Who reads it

Two consumers, and they behave differently:

1. The planner. Its instruction is literally to walk the graph of available_from hints to build the command sequence. The hints are the only structured statement of "you must call X before Y", so an unhinted handle parameter is a parameter the planner has to guess its way to.
2. The missing-parameter message. When validation finds the field absent, it appends use the <producers> command(s) to get <field> information. A human caller is told to abort and use ...; an agent (run_as_agent set on the workflow context) is told to just use it, because the agent can chain without abandoning the turn.

Only Input fields are read. Putting the hint on an Output field does nothing.

The hint is surfaced only when the field is missing, so it never substitutes for description — write both.

Rule 1 — name a producer the caller can actually reach

A hint naming a command the caller cannot invoke is worse than no hint: it sends the planner down a path that dead-ends. Reachable means either

• on the calling context's own surface, own or inherited, or
• on a live ancestor's surface, since a wildcard prediction escalates up the runtime parent chain and serves the command there without a navigation turn.