MCP Weather Service

Instructions

Implementation Reference

• src/index.ts:178-238 (registration)

  Registers the 'get-weather' tool using server.tool() with name, description, input schema using Zod, and inline handler function.

  server.tool(
    'get-weather', 
    'Get weather information for a city', 
    {
      city: z.string().describe('City name to get weather for')
    }, 
    async ({ city }) => {
      debug(`Handling get-weather request for city: ${city}`);
      
      try {
        let attempts = 0;
        const maxAttempts = 3;
        let lastError: Error | null = null;
        
        while (attempts < maxAttempts) {
          try {
            attempts++;
            debug(`Attempt ${attempts}/${maxAttempts} for city: ${city}`);
            
            // 最後の試行では、可能であればモックデータを使用
            const useMockData = attempts === maxAttempts;
            const weather = await getWeatherForCity(city, useMockData);
            
            const conditionJapanese = weather.condition;
            
            return {
              content: [{
                type: 'text',
                text: `${weather.cityName}の天気:\n気温: ${weather.temperature}\n状態: ${conditionJapanese}`
              }]
            };
          } catch (error) {
            lastError = error instanceof Error ? error : new Error(String(error));
            debug(`Attempt ${attempts} failed:`, lastError.message);
            
            if (attempts < maxAttempts) {
              const waitTime = 1000 * attempts;
              debug(`Waiting ${waitTime}ms before next retry`);
              await new Promise(resolve => setTimeout(resolve, waitTime));
            }
          }
        }
        
        return {
          content: [{
            type: 'text',
            text: `${city}の天気情報の取得に失敗しました: ${lastError?.message || '不明なエラー'}`
          }]
        };
      } catch (error) {
        debug(`Error processing weather request:`, error);
        
        return {
          content: [{
            type: 'text',
            text: `${city}の天気情報の取得に失敗しました: ${error instanceof Error ? error.message : String(error)}`
          }]
        };
      }
    }
  );

• src/index.ts:184-237 (handler)

  Handler function implementing the 'get-weather' tool logic: retries API calls via getWeatherForCity, handles errors, formats response as MCP text content.

  async ({ city }) => {
    debug(`Handling get-weather request for city: ${city}`);
    
    try {
      let attempts = 0;
      const maxAttempts = 3;
      let lastError: Error | null = null;
      
      while (attempts < maxAttempts) {
        try {
          attempts++;
          debug(`Attempt ${attempts}/${maxAttempts} for city: ${city}`);
          
          // 最後の試行では、可能であればモックデータを使用
          const useMockData = attempts === maxAttempts;
          const weather = await getWeatherForCity(city, useMockData);
          
          const conditionJapanese = weather.condition;
          
          return {
            content: [{
              type: 'text',
              text: `${weather.cityName}の天気:\n気温: ${weather.temperature}\n状態: ${conditionJapanese}`
            }]
          };
        } catch (error) {
          lastError = error instanceof Error ? error : new Error(String(error));
          debug(`Attempt ${attempts} failed:`, lastError.message);
          
          if (attempts < maxAttempts) {
            const waitTime = 1000 * attempts;
            debug(`Waiting ${waitTime}ms before next retry`);
            await new Promise(resolve => setTimeout(resolve, waitTime));
          }
        }
      }
      
      return {
        content: [{
          type: 'text',
          text: `${city}の天気情報の取得に失敗しました: ${lastError?.message || '不明なエラー'}`
        }]
      };
    } catch (error) {
      debug(`Error processing weather request:`, error);
      
      return {
        content: [{
          type: 'text',
          text: `${city}の天気情報の取得に失敗しました: ${error instanceof Error ? error.message : String(error)}`
        }]
      };
    }
  }

• src/index.ts:181-183 (schema)

  Zod input schema defining the 'city' parameter as a required string.

  {
    city: z.string().describe('City name to get weather for')
  }, 

• src/index.ts:94-156 (helper)

  Helper function to fetch real weather data from Open-Meteo APIs (geocoding + forecast) or use mock data, translates weather codes to Japanese.

  async function getWeatherForCity(city: string, useMockData: boolean = false) {
    try {
      const normalizedCity = city.trim();
      debug(`Getting weather for city: ${normalizedCity}`);
      
      if (useMockData && MOCK_WEATHER_DATA[normalizedCity]) {
        debug(`Using mock data for ${normalizedCity}`);
        return MOCK_WEATHER_DATA[normalizedCity];
      }
      
      // ジオコーディングAPIを使用して座標を取得
      const geocodingResponse = await axios.get(
        `https://geocoding-api.open-meteo.com/v1/search`,
        {
          params: {
            name: normalizedCity,
            count: 1,
            language: 'en'
          },
          timeout: 5000
        }
      );
      
      if (!geocodingResponse.data.results || geocodingResponse.data.results.length === 0) {
        throw new Error(`City "${normalizedCity}" not found`);
      }
      
      const { latitude, longitude, name } = geocodingResponse.data.results[0];
      debug(`Found coordinates for ${name}: ${latitude}, ${longitude}`);
      
      // 天気APIを使用して天気情報を取得
      const weatherResponse = await axios.get(
        `https://api.open-meteo.com/v1/forecast`,
        {
          params: {
            latitude,
            longitude,
            current: 'temperature_2m,weather_code',
            timezone: 'Asia/Tokyo'
          },
          timeout: 5000
        }
      );
      
      const weatherCode = weatherResponse.data.current.weather_code;
      const weatherDescription = weatherCodes[weatherCode] || "不明";
      
      return {
        cityName: name,
        temperature: `${weatherResponse.data.current.temperature_2m}${weatherResponse.data.current_units.temperature_2m}`,
        condition: weatherDescription
      };
    } catch (error) {
      debug(`Error getting weather for city ${city}:`, error);
      
      if (MOCK_WEATHER_DATA[city]) {
        debug(`Falling back to mock data for ${city}`);
        return MOCK_WEATHER_DATA[city];
      }
      
      throw error;
    }
  }