Weather MCP Server

Instructions

Implementation Reference

• src/weather-service.ts:31-44 (handler)

  Core handler function that implements the get_weather_forecast tool logic. Normalizes location, fetches from mock data if available, or generates synthetic forecast.

  async getWeatherForecast(location: string, days: number = 3): Promise<WeatherForecast> {
    const normalizedLocation = this.normalizeLocation(location);
    
    if (mockForecastData[normalizedLocation]) {
      const forecast = mockForecastData[normalizedLocation];
      return {
        ...forecast,
        forecast: forecast.forecast.slice(0, days)
      };
    }
    
    // If location not found, generate mock forecast data
    return this.generateMockForecast(location, days);
  }

• src/types.ts:15-28 (schema)

  TypeScript interface definitions for the WeatherForecast output type used by the tool.

  export interface WeatherForecast {
    location: string;
    forecast: DailyForecast[];
  }
  
  export interface DailyForecast {
    date: string;
    highTemp: number;
    lowTemp: number;
    condition: string;
    description: string;
    chanceOfRain: number;
    humidity: number;
  }

• src/index.ts:53-71 (registration)

  Tool registration in the main stdio MCP server (index.ts), defining name, description, and input schema for ListTools response.

    name: 'get_weather_forecast',
    description: 'Get weather forecast for a specified location',
    inputSchema: {
      type: 'object',
      properties: {
        location: {
          type: 'string',
          description: 'Location name',
        },
        days: {
          type: 'number',
          description: 'Forecast days (1-7 days, default is 3 days)',
          minimum: 1,
          maximum: 7,
        },
      },
      required: ['location'],
    },
  },

• src/sse-server.ts:42-59 (registration)

  Tool registration in the SSE MCP server.

  name: "get_weather_forecast",
  description: "Get weather forecast for a specified location",
  inputSchema: {
    type: "object",
    properties: {
      location: {
        type: "string",
        description: "Location name",
      },
      days: {
        type: "number",
        description: "Forecast days (1-7 days, default 3 days)",
        minimum: 1,
        maximum: 7,
      },
    },
    required: ["location"],
  },

• src/weather-service.ts:124-158 (helper)

  Private helper method called by the handler to generate synthetic forecast data when no mock data is available for the location.

  private generateMockForecast(location: string, days: number): WeatherForecast {
    const forecast = [];
    const baseTemp = 20 + Math.random() * 15; // Temperature between 20-35°C
    const conditions = ['Sunny', 'Partly Cloudy', 'Cloudy', 'Rainy', 'Thunderstorms', 'Overcast', 'Light Rain'];
    const descriptions = {
      'Sunny': 'Clear skies with bright sunshine',
      'Partly Cloudy': 'Mix of sun and clouds',
      'Cloudy': 'Overcast skies with mild temperatures',
      'Rainy': 'Rain showers expected',
      'Thunderstorms': 'Thunderstorms with heavy rain',
      'Overcast': 'Cloudy skies throughout the day',
      'Light Rain': 'Light rain showers'
    };
    
    for (let i = 1; i <= days; i++) {
      const date = new Date(Date.now() + i * 24 * 60 * 60 * 1000);
      const tempVariation = (Math.random() - 0.5) * 10;
      const condition = conditions[Math.floor(Math.random() * conditions.length)];
      
      forecast.push({
        date: date.toISOString().split('T')[0],
        highTemp: Math.round(baseTemp + tempVariation + 5),
        lowTemp: Math.round(baseTemp + tempVariation - 5),
        condition,
        description: descriptions[condition as keyof typeof descriptions] || `${condition} conditions expected`,
        chanceOfRain: condition.includes('Rain') || condition.includes('Thunder') ? 70 + Math.random() * 30 : Math.random() * 40,
        humidity: 50 + Math.random() * 40
      });
    }
    
    return {
      location,
      forecast
    };
  }