Design a useful MCP server
Shape clear capability definitions, schemas, outputs, and errors.
- Design an MCP capability that is understandable and predictable for clients.
A useful server has a clear purpose and exposes only the capabilities needed for it. Tool names and descriptions should state what an action does, arguments should have explicit schemas, and results should be structured and unambiguous. Validate inputs at the server boundary, return actionable errors, and avoid hiding important side effects behind vague descriptions.
A small example
1tool = {
2 "name": "lookup_order",
3 "input": {"order_id": "string"},
4 "effect": "read-only lookup",
5}
6print(tool["name"], tool["input"]["order_id"], tool["effect"])lookup_order string read-only lookup
Design for the client that has to choose and call the capability: specific descriptions reduce ambiguity, and schemas make expected input explicit. Keep server errors useful without exposing secrets. For actions that modify data, make the effect clear and consider idempotency and confirmation needs.
Key takeaways
Design an MCP capability that is understandable and predictable for clients.
Keep capability access explicit and handle results as untrusted input.
Lesson quiz
5 questions · pass with 4 correct · up to 50 XP
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