The Weather MCP server has two tools with basic structure but significant quality gaps. Both tools use proper verb_noun naming (get_*) and have simple input schemas with Zod validation. However, descriptions are minimal (under 60 chars), parameter descriptions lack detail, output schemas are completely undocumented, and error handling is absent. Tool outputs are returned as JSON strings embedded in text fields rather than structured objects, violating the response-shaper pattern. No pagination support, no result limits documented, and no guidance on when to use each tool. The server is functional but falls well short of production-grade tool quality.
Tool descriptions are too short and lack context. Both tools have descriptions under 50 characters with no explanation of WHEN to use each tool or WHAT it returns. Description for 'get-current-weather-by-city' is 39 chars; baseline minimum is 50-60 chars, and A+ tools average 194 chars.
Parameter 'city' lacks meaningful description. The description 'Name of the city' is generic and does not specify format constraints, valid values, or examples. Should clarify: is it a city name only? Does it require country/state? What's the max length?
Output schema is completely undocumented. Both tools return JSON strings embedded in text content type, but there is no explicit schema definition telling LLMs what fields to expect. Response should document: fields like 'cityName', 'conditions', 'temperature', 'windSpeed' are present, types, and units (e.g., Celsius vs Fahrenheit).
Recommendations
Expand tool descriptions to 80-150 characters minimum, following pattern: 'Get [WHAT] by [HOW]. Use this when [WHEN]. Returns [FIELDS].' Example: 'Get current weather conditions (temperature, wind, precipitation) for a city. Use this to answer questions like "What's the weather in NYC?" Returns structured object with cityName, conditions, temperature (°C), windSpeed (kph), windDirection.'
Add constraint descriptions to 'city' parameter: 'City name (case-insensitive, e.g. "London", "Tokyo"). Max 100 chars. If city not found, tool returns error listing available nearby cities.'
Add explicit output schema documentation in each tool definition. Document: 'Returns { cityName: string, conditions: 'Sunny'|'Cloudy'|..., temperature: number (°C), windSpeed: number (kph), windDirection: string, humidity: number (%), feelsLike: number (°C) }'
Implement error handling: validate city input, catch API errors, return actionable messages like 'City "xyz" not found. Available cities: London, Paris, Berlin. Try one of these?' rather than silent failures or generic errors.
Add distinguishing descriptions: 'get-current-weather-by-city: Returns TODAY'S conditions (temperature, wind, precipitation, humidity). Use for immediate weather questions.' vs 'get-weather-forecast-by-city: Returns 5-7 day forecast with daily high/low temps and conditions. Use to plan future activities or check upcoming weather.'
Output format violates structured response pattern. Tools return raw JSON as a text string rather than as structured object properties. This forces LLMs to parse unstructured text, which is error-prone, wastes tokens, and increases hallucination risk. Should return typed object with fields like {cityName: string, conditions: string, temperature: number} rather than stringified JSON.
No error handling or recovery guidance. Handlers have no try-catch, input validation, or error messages telling LLMs what to do if city is not found, malformed, or invalid. Missing error classification (retryable vs. user-fixable).
Distinction between tools unclear. Both tools retrieve weather but one is 'current' and one is 'forecast'. Tool descriptions do not explain the difference or when to use each. LLMs may conflate them or call both when only one is needed.
No tool composition support. If downstream tools need weather data in a specific format (e.g., structured JSON with units), the current text-string output cannot be chained reliably. Output should return typed object with consistent field names and units.
Mock/hardcoded data only. Both tools return hardcoded JSON responses (e.g., 'Sun', 12°, 8 mph) regardless of input city. This is a proof-of-concept, not a production tool. No actual weather API integration; tool cannot fulfill its stated purpose.
If implementing real API: integrate with OpenWeatherMap, WeatherAPI, or similar; validate responses; cache results to reduce API calls; document rate limits and timeout behavior.
Add parameter validation: reject cities with special chars, enforce length limits (1-100 chars), case-normalize input before lookup to improve match rates.
Consider adding optional parameters for future enhancement: units (celsius|fahrenheit), lang (en|es|fr), and response format (minimal|detailed) to support varied use cases.