MCP Servers

Instructions

Implementation Reference

• src/weather/controllers/weather.ts:27-46 (handler)

  Main implementation of the get-forecast tool logic: fetches raw forecast data from service and formats it into a readable 5-day text summary.

  async getForecast(city: string, country?: string): Promise<string> {
    const forecastData = await this.weatherService.getForecast(city, country);
  
    if (!forecastData) {
      return `Failed to retrieve forecast data for ${country ? `${city}, ${country}` : city}`;
    }
  
    const forecasts = forecastData.list
      .filter((_, index) => index % 8 === 0) // Get one forecast per day
      .map(forecast => [
        `\nDate: ${forecast.dt_txt.split(" ")[0]}`,
        `Temperature: ${forecast.main.temp}°C (Feels like: ${forecast.main.feels_like}°C)`,
        `Conditions: ${forecast.weather[0].main} - ${forecast.weather[0].description}`,
        `Humidity: ${forecast.main.humidity}%`,
        `Wind Speed: ${forecast.wind.speed} m/s`,
        "---"
      ].join("\n"));
  
    return `5-day forecast for ${forecastData.city.name}, ${forecastData.city.country}:\n${forecasts.join("\n")}`;
  }

• src/weather/index.ts:42-60 (registration)

  Registers the 'get-forecast' MCP tool with description, input schema (Zod), and handler that delegates to WeatherController.getForecast().

  server.tool(
    "get-forecast",
    "Get 5-day weather forecast for a location",
    {
      city: z.string().describe("City name (e.g. Beijing, London)"),
      country: z.string().optional().describe("Country code (e.g. CN, GB)")
    },
    async ({ city, country }) => {
      const forecastText = await weatherController.getForecast(city, country);
      return {
        content: [
          {
            type: "text",
            text: forecastText,
          },
        ],
      };
    }
  );

• src/weather/service/weather.ts:40-43 (helper)

  Helper method in WeatherService that constructs the API query and fetches raw forecast data from OpenWeatherMap.

  async getForecast(city: string, country?: string): Promise<ForecastData | null> {
    const query = country ? `${city},${country}` : city;
    return this.makeRequest<ForecastData>("forecast", { q: query });
  }

• src/weather/service/types.ts:22-43 (schema)

  TypeScript interface defining the structure of the OpenWeather forecast response data for type safety.

  export interface ForecastData {
    list: Array<{
      dt_txt: string;
      main: {
        temp: number;
        feels_like: number;
        humidity: number;
      };
      weather: Array<{
        main: string;
        description: string;
      }>;
      wind: {
        speed: number;
        deg: number;
      };
    }>;
    city: {
      name: string;
      country: string;
    };
  }