The server provides ONE tool (sum) with a clear, concise description and well-formed JSON Schema. Naming is direct and action-oriented (verb+noun). The schema includes proper types (array of numbers) and a parameter description. However, the server is minimal (single-tool example), lacks error handling guidance, and provides no output schema documentation. The description is adequate (72 chars) but could articulate when/why to use this tool more explicitly for LLM decision-making. Schema is complete with type and description, avoiding the common pitfall of omitted parameter documentation. No evidence of security patterns, composition guidance, or idempotent operation markers.

• Add an explicit output schema in the tool definition. Document the exact response structure, e.g., 'Returns a JSON object: {"sum": <number>, "count": <number>, "is_valid": <boolean>}'.
• Expand the description to 150 - 200 characters explaining WHAT (calculates sum), WHEN to use (numeric aggregation), and WHAT to expect in the response. Reference pattern:tool-description.
• Add constraints to the 'values' parameter: 'A non-empty array of finite numbers (no NaN, no Infinity). Array length must be between 1 and 10,000.'
• Include error guidance in the description: 'Returns an error if any value is NaN, Infinity, or non-numeric. If this occurs, validate inputs and retry with finite numbers only.'
• Consider adding optional parameters like 'precision' (number of decimal places) or 'exclude_nulls' (boolean) to increase tool flexibility without breaking the core contract.