Single tool 'add_numbers' has a complete input schema with proper types and descriptions for both parameters. However, the tool description is minimal (24 chars), and critically, there is NO documented output schema. The server lacks error handling guidance, parameter validation rules, and any indication of idempotency or side effects. The implementation is functional but falls well short of production-grade tool design. No tool annotations (readOnlyHint, destructiveHint, idempotentHint) are present.

• Expand tool description to 100-200 characters explaining WHAT the tool does, WHEN to use it (e.g., 'for arithmetic calculations'), and WHAT it returns (a numeric sum). Example: 'Add two numbers together and return their sum. Use this for arithmetic calculations. Returns a single numeric result.'
• Document the output schema explicitly: {"type": "object", "properties": {"result": {"type": "number", "description": "The sum of the two input numbers"}}, "required": ["result"]}
• Add parameter constraints: 'a' and 'b' should document acceptable ranges (e.g., 'A number between -1e308 and 1e308') and precision expectations.
• Implement structured error responses with recovery guidance. Example: {"error": "Invalid input: 'a' must be a number, got string", "recovery": "Ensure both parameters are numeric values."}
• Add tool annotations to the schema: include 'readOnlyHint': true (since addition has no side effects) and 'idempotentHint': true (same inputs always produce same output).