10. Require a field only when another is present

reason is meaningless without stage_id. You want "if stage_id is provided, reason becomes required" — without making either unconditionally required.

Problem. reason is meaningless without stage_id. You want "if stage_id is provided, reason becomes required" — without making either unconditionally required.

Solution. @depends_on(:other_field). It emits JSON Schema dependentRequired.

#: (
#:   workflow_id: String,
#:   ?stage_id: String?   @requires(:backward_routing) @depends_on(:workflow_id),
#:   ?reason: String?     @requires(:backward_routing) @depends_on(:stage_id)
#: ) -> Hash[Symbol, untyped]

Result. For a manager, the schema includes:

{ "dependentRequired": { "workflow_id": ["stage_id"], "stage_id": ["reason"] } }

Note both fields are also gated by @requires — tags stack and AND together. An operator sees neither field nor the dependency.

Collected from COOKBOOK.md in the repository. Edit it there, not here.