MCP builder

Design principles

• One capability per tool — clear name, single purpose.
• Strict schemas — JSON Schema for inputs; document required vs optional.
• Predictable errors — machine-readable codes + human message; no stack traces to client by default.
• Idempotent reads — writes clearly labeled; confirm destructive ops in description.

Server checklist

• server identity and version documented
• Tool list small and discoverable
• Input validation before side effects
• Timeouts and size limits on responses
• Auth documented (env vars, OAuth, local only)
• README: install, config, example tool calls

Tool definition pattern