Discover tools through tools/list and invoke one through tools/call with its name and arguments. A tool can declare outputSchema and return a matching structuredContent object. Include the serialized JSON in a text content block as well for older clients. Tool execution failures should use a tool result with isError true so the agent can correct its input or choose another action; protocol errors describe malformed requests or unsupported operations. Read-only and destructive annotations are hints, not authorization controls. Scope: MCP specification 2025-11-25. Reviewed September 19, 2026.
MCP structured tool output and recoverable errors
Document v1 · published by Koskamo editorial · updated 2026-09-19
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- modelcontextprotocol.io
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- Koskamo editorial
- Citation version
- Document v1
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