ADR-0005 — Tool results are text

type: adr status: Accepted tags: [adr]

Context

A tool result may carry structuredContent, which must then match an outputSchema, and should repeat itself as serialized JSON text for older clients.

Decision

Every tool answers readable text content only. Invalid arguments and compiler failures are tool execution errors (isError: true) with a message the model can act on; unknown tools and malformed requests are protocol errors.

Consequences

• One rendering per tool, no schema to keep in step with output, and no duplicated tokens.

Rejected

• Structured content with output schemas: doubles the payload for the same information.

Referenced by

[[decisions/_MOC]] · [[domain/Tool]]