MCP Weather Server

Instructions

Implementation Reference

• main.ts:598-639 (handler)

  The MCP tool handler function. Calls getAirQualityForCity, handles result or error, and returns formatted MCP content (text error or JSON data).
  async({ city }) => { try { const result = await getAirQualityForCity(city); // If it's an error string, return it as text if (typeof result === 'string') { return { content: [ { type: "text", text: result } ] }; } // If it's processed data, return it as JSON string for structured access return { content: [ { type: "text", text: JSON.stringify(result, null, 2) } ] }; } catch (error) { console.error('Air quality fetch error:', error); const errorMessage = error instanceof Error && error.message.includes('fetch') ? `❌ Unable to fetch air quality data. Please check your internet connection and try again.` : `❌ Error: ${error instanceof Error ? error.message : 'Unknown error'}`; return { content: [ { type: "text", text: errorMessage } ] }; } }
• main.ts:409-472 (helper)

  Core helper function implementing the air quality tool logic: geocodes city, fetches current and hourly European AQI data from APIs, processes into structured format with location, current, hourly, and raw data.
  async function getAirQualityForCity(city: string): Promise<ProcessedAirQualityData | string> { // Step 1: Get coordinates for the city const geoUrl = `${CONFIG.GEOCODING_API}?name=${encodeURIComponent(city)}&count=1&language=en&format=json`; const geoResponse = await fetchWithRetry(geoUrl); const geoData: GeocodingResponse = await geoResponse.json(); // Handle city not found if (!geoData.results || geoData.results.length === 0) { return `❌ Sorry, I couldn't find a city named "${city}". Please check the spelling and try again.`; } const location = geoData.results[0]; // Step 2: Get air quality data const aqiUrl = `${CONFIG.AIR_QUALITY_API}?latitude=${location.latitude}&longitude=${location.longitude}&hourly=european_aqi,european_aqi_pm2_5,european_aqi_pm10,european_aqi_no2,european_aqi_o3,european_aqi_so2&current=european_aqi,european_aqi_pm2_5,european_aqi_pm10,european_aqi_no2,european_aqi_o3,european_aqi_so2`; const aqiResponse = await fetchWithRetry(aqiUrl); const aqiData: AirQualityResponse = await aqiResponse.json(); // Process and structure the air quality data const locationName = location.admin1 ? `${location.name}, ${location.admin1}, ${location.country}` : `${location.name}, ${location.country}`; const current = aqiData.current; const aqiInfo = getAqiLevel(current.european_aqi); const processedData: ProcessedAirQualityData = { location: { name: location.name, fullName: locationName, latitude: location.latitude, longitude: location.longitude, country: location.country, admin1: location.admin1 }, current: { time: current.time, formattedTime: formatTime(current.time), europeanAqi: current.european_aqi, aqiLevel: aqiInfo.level, aqiDescription: aqiInfo.description, pm25: current.european_aqi_pm2_5, pm10: current.european_aqi_pm10, no2: current.european_aqi_no2, o3: current.european_aqi_o3, so2: current.european_aqi_so2 }, hourly: aqiData.hourly.time.slice(0, 24).map((time, index) => { const aqi = aqiData.hourly.european_aqi[index]; const aqiInfo = getAqiLevel(aqi); return { time: time, formattedTime: formatTime(time), europeanAqi: aqi, aqiLevel: aqiInfo.level, pm25: aqiData.hourly.european_aqi_pm2_5[index], pm10: aqiData.hourly.european_aqi_pm10[index], no2: aqiData.hourly.european_aqi_no2[index], o3: aqiData.hourly.european_aqi_o3[index], so2: aqiData.hourly.european_aqi_so2[index] }; }), raw: aqiData }; return processedData; }
• main.ts:588-640 (registration)

  Registration of the 'get-air-quality' tool on the MCP server, specifying name, description, input schema, and handler.
  // Register the air quality tool server.tool( 'get-air-quality', 'Get air pollution data for any city including European Air Quality Index and pollutant levels', { city: z.string() .min(1, "City name cannot be empty") .max(100, "City name is too long") .describe("The name of the city to get air quality information for (e.g., 'New York', 'London', 'Tokyo')") }, async({ city }) => { try { const result = await getAirQualityForCity(city); // If it's an error string, return it as text if (typeof result === 'string') { return { content: [ { type: "text", text: result } ] }; } // If it's processed data, return it as JSON string for structured access return { content: [ { type: "text", text: JSON.stringify(result, null, 2) } ] }; } catch (error) { console.error('Air quality fetch error:', error); const errorMessage = error instanceof Error && error.message.includes('fetch') ? `❌ Unable to fetch air quality data. Please check your internet connection and try again.` : `❌ Error: ${error instanceof Error ? error.message : 'Unknown error'}`; return { content: [ { type: "text", text: errorMessage } ] }; } } );
• main.ts:592-597 (schema)

  Input schema using Zod for validating the 'city' parameter.
  { city: z.string() .min(1, "City name cannot be empty") .max(100, "City name is too long") .describe("The name of the city to get air quality information for (e.g., 'New York', 'London', 'Tokyo')") },
• main.ts:261-294 (schema)

  TypeScript interface defining the structure of processed air quality data returned by the tool.
  interface ProcessedAirQualityData { location: { name: string; fullName: string; latitude: number; longitude: number; country: string; admin1?: string; }; current: { time: string; formattedTime: string; europeanAqi: number; aqiLevel: string; aqiDescription: string; pm25: number; pm10: number; no2: number; o3: number; so2: number; }; hourly: Array<{ time: string; formattedTime: string; europeanAqi: number; aqiLevel: string; pm25: number; pm10: number; no2: number; o3: number; so2: number; }>; raw: AirQualityResponse; }