Weather Server

A simple weather server

Here's the js code for a simple weather server using the weather.gov api

const { McpServer } = require("@modelcontextprotocol/sdk/server/mcp.js");
const { StdioServerTransport } = require("@modelcontextprotocol/sdk/server/stdio.js");
const { z } = require("zod");

const NWS_API_BASE = "https://api.weather.gov";
const USER_AGENT = "weather-app/1.0";

async function makeNWSRequest(url) {
  const headers = {
    "User-Agent": USER_AGENT,
    Accept: "application/geo+json",
  };

  try {
    const response = await fetch(url, { headers });
    if (!response.ok) {
      throw new Error(`HTTP error! status: ${response.status}`);
    }
    return await response.json();
  } catch (error) {
    console.error("Error making NWS request:", error);
    return null;
  }
}
function formatAlert(feature) {
  const props = feature.properties;
  return [
    `Event: ${props.event || "Unknown"}`,
    `Area: ${props.areaDesc || "Unknown"}`,
    `Severity: ${props.severity || "Unknown"}`,
    `Status: ${props.status || "Unknown"}`,
    `Headline: ${props.headline || "No headline"}`,
    "---",
  ].join("\n");
}



// Create server instance
const server = new McpServer({
  name: "weather",
  version: "1.0.0",
});

// Register weather tools
server.tool(
  "get-alerts",
  "Get weather alerts for a state",
  {
    state: z.string().length(2).describe("Two-letter state code (e.g. CA, NY)"),
  },
  async ({ state }) => {
    const stateCode = state.toUpperCase();
    const alertsUrl = `${NWS_API_BASE}/alerts?area=${stateCode}`;
    const alertsData = await makeNWSRequest(alertsUrl);

    if (!alertsData) {
      return {
        content: [
          {
            type: "text",
            text: "Failed to retrieve alerts data",
          },
        ],
      };
    }

    const features = alertsData.features || [];
    if (features.length === 0) {
      return {
        content: [
          {
            type: "text",
            text: `No active alerts for ${stateCode}`,
          },
        ],
      };
    }

    const formattedAlerts = features.map(formatAlert);
    const alertsText = `Active alerts for ${stateCode}:\n\n${formattedAlerts.join("\n")}`;

    return {
      content: [
        {
          type: "text",
          text: alertsText,
        },
      ],
    };
  },
);

server.tool(
  "get-forecast",
  "Get weather forecast for a location",
  {
    latitude: z.number().min(-90).max(90).describe("Latitude of the location"),
    longitude: z
      .number()
      .min(-180)
      .max(180)
      .describe("Longitude of the location"),
  },
  async ({ latitude, longitude }) => {
    // Get grid point data
    const pointsUrl = `${NWS_API_BASE}/points/${latitude.toFixed(4)},${longitude.toFixed(4)}`;
    const pointsData = await makeNWSRequest(pointsUrl);

    if (!pointsData) {
      return {
        content: [
          {
            type: "text",
            text: `Failed to retrieve grid point data for coordinates: ${latitude}, ${longitude}. This location may not be supported by the NWS API (only US locations are supported).`,
          },
        ],
      };
    }

    const forecastUrl = pointsData.properties?.forecast;
    if (!forecastUrl) {
      return {
        content: [
          {
            type: "text",
            text: "Failed to get forecast URL from grid point data",
          },
        ],
      };
    }

    // Get forecast data
    const forecastData = await makeNWSRequest(forecastUrl);
    if (!forecastData) {
      return {
        content: [
          {
            type: "text",
            text: "Failed to retrieve forecast data",
          },
        ],
      };
    }

    const periods = forecastData.properties?.periods || [];
    if (periods.length === 0) {
      return {
        content: [
          {
            type: "text",
            text: "No forecast periods available",
          },
        ],
      };
    }

    // Format forecast periods
    const formattedForecast = periods.map((period) =>
      [
        `${period.name || "Unknown"}:`,
        `Temperature: ${period.temperature || "Unknown"}°${period.temperatureUnit || "F"}`,
        `Wind: ${period.windSpeed || "Unknown"} ${period.windDirection || ""}`,
        `${period.shortForecast || "No forecast available"}`,
        "---",
      ].join("\n"),
    );

    const forecastText = `Forecast for ${latitude}, ${longitude}:\n\n${formattedForecast.join("\n")}`;

    return {
      content: [
        {
          type: "text",
          text: forecastText,
        },
      ],
    };
  },
);

// Start the server
async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
  console.error("Weather MCP Server running on stdio");
}

main().catch((error) => {
  console.error("Fatal error in main():", error);
  process.exit(1);
});

This example is adapted from https://github.com/modelcontextprotocol/quickstart-resources/tree/main/weather-server-typescript