Single tool with critical definition gaps. Tool name 'query_exchange_rates' is acceptable (verb_noun pattern), but descriptions are severely deficient. No output schema documented, return type is `list[types.TextContent | types.ImageContent | types.EmbeddedResource]` but actual structure (fields, format) is undocumented. No error handling guidance. No input validation or constraints (e.g., currency code format, length). Missing critical metadata: no indication of API rate limits, required authentication, or failure modes.

• Provide English-language descriptions for tool and all parameters. Example: 'Query real-time currency exchange rates between two ISO 4217 currency codes. Returns the current exchange rate and timestamp.'
• Replace example values with formal constraints. Change parameter descriptions to: 'from_code: ISO 4217 three-letter currency code (uppercase, e.g., CNY, USD, EUR). Length: exactly 3 characters.' Use enum if only specific currencies are supported.
• Document the output schema explicitly. Specify: response structure (e.g., {rate: float, from: string, to: string, timestamp: string}), field types, and error response format.
• Add error handling with recovery guidance. Example: 'If error_code != 0, return: "Exchange rate lookup failed: {reason}. Verify currency codes are valid ISO 4217 codes (e.g., USD, EUR, CNY)."'
• Validate API key at server startup and return a clear error if missing. Document required environment variable in README with setup instructions.