Prescribe a minimal output schema for ONE agent's handoff to its controller — the `model-right-sizer` agent's "Agent-to-agent message-schema design" lever, scoped to a single seam instead of a whole flow's blueprint. Given a target agent (a path to an existing agent `.md` file, or a description of one not yet written), returns a schema-conformant JSON prescription (`schemas/agent-schema.schema.json`) naming the reusable family the agent's reply fits, typed `in`/`out` fields, an exclusion list, and a ready-to-insert `## Agent-to-agent schema` markdown stamp — reproduced here in portable, organization-agnostic form. Offers to stamp that block directly into the target agent's file, idempotently. The point: an agent that used to hand its controller unscoped prose now hands it typed fields plus one bounded prose slot. Use when someone says "give this agent an output schema", "prescribe a schema for …", "minimize what this agent returns", or "stamp an agent-to-agent contract on …".