Weather MCP Server

Instructions

Implementation Reference

• index.js:156-195 (handler)

  The handler function that implements the get_current_weather tool by fetching data from the OpenWeatherMap API, handling errors, formatting the weather information into a user-friendly text response, and returning it in the MCP content format.

    async getCurrentWeather(city, units = 'metric') {
      const url = `${API_BASE_URL}/weather?q=${encodeURIComponent(city)}&units=${units}&appid=${API_KEY}`;
  
      const response = await fetch(url);
  
      if (!response.ok) {
        if (response.status === 404) {
          throw new Error(`City "${city}" not found`);
        }
        throw new Error(`Weather API error: ${response.statusText}`);
      }
  
      const data = await response.json();
  
      // Format the response
      const tempUnit = units === 'metric' ? '°C' : '°F';
      const speedUnit = units === 'metric' ? 'm/s' : 'mph';
  
      const weatherText = `
  🌤️ Current Weather in ${data.name}, ${data.sys.country}
  
  Temperature: ${data.main.temp}${tempUnit} (feels like ${data.main.feels_like}${tempUnit})
  Condition: ${data.weather[0].main} - ${data.weather[0].description}
  Humidity: ${data.main.humidity}%
  Wind Speed: ${data.wind.speed} ${speedUnit}
  Pressure: ${data.main.pressure} hPa
  Visibility: ${(data.visibility / 1000).toFixed(1)} km
  
  Last updated: ${new Date(data.dt * 1000).toLocaleString()}
      `.trim();
  
      return {
        content: [
          {
            type: 'text',
            text: weatherText,
          },
        ],
      };
    }

• index.js:80-95 (schema)

  Input schema for the get_current_weather tool, defining the expected parameters: city (required string) and units (optional string enum: metric or imperial, default metric).

  inputSchema: {
    type: 'object',
    properties: {
      city: {
        type: 'string',
        description: 'City name (e.g., "Taipei", "Tokyo", "New York")',
      },
      units: {
        type: 'string',
        description: 'Temperature units: "metric" (Celsius) or "imperial" (Fahrenheit)',
        enum: ['metric', 'imperial'],
        default: 'metric',
      },
    },
    required: ['city'],
  },

• index.js:77-96 (registration)

  Registration of the get_current_weather tool in the ListToolsRequestSchema handler, providing name, description, and input schema.

  {
    name: 'get_current_weather',
    description: 'Get current weather information for a specific city',
    inputSchema: {
      type: 'object',
      properties: {
        city: {
          type: 'string',
          description: 'City name (e.g., "Taipei", "Tokyo", "New York")',
        },
        units: {
          type: 'string',
          description: 'Temperature units: "metric" (Celsius) or "imperial" (Fahrenheit)',
          enum: ['metric', 'imperial'],
          default: 'metric',
        },
      },
      required: ['city'],
    },
  },

• index.js:126-127 (registration)

  Registration/dispatch logic in the CallToolRequestSchema handler that maps tool calls for 'get_current_weather' to the handler function.

  case 'get_current_weather':
    return await this.getCurrentWeather(args.city, args.units || 'metric');