import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { z } from "zod";
import express from "express";
import { randomUUID } from "node:crypto";
import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js";
const NWS_API_BASE = "https://api.weather.gov";
const USER_AGENT = "weather-app/1.0";
// Helper function for making NWS API requests
async function makeNWSRequest<T>(url: string): Promise<T | null> {
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()) as T;
} catch (error) {
console.error("Error making NWS request:", error);
return null;
}
}
interface AlertFeature {
properties: {
event?: string;
areaDesc?: string;
severity?: string;
status?: string;
headline?: string;
};
}
// Format alert data
function formatAlert(feature: AlertFeature): string {
const props = feature.properties;
return [
`Event: ${props.event || "Unknown"}`,
`Area: ${props.areaDesc || "Unknown"}`,
`Severity: ${props.severity || "Unknown"}`,
`Status: ${props.status || "Unknown"}`,
`Headline: ${props.headline || "No headline"}`,
"---",
].join("\n");
}
interface ForecastPeriod {
name?: string;
temperature?: number;
temperatureUnit?: string;
windSpeed?: string;
windDirection?: string;
shortForecast?: string;
}
interface AlertsResponse {
features: AlertFeature[];
}
interface PointsResponse {
properties: {
forecast?: string;
};
}
interface ForecastResponse {
properties: {
periods: ForecastPeriod[];
};
}
// Create and configure MCP server with weather tools
function createServer(): McpServer {
const server = new McpServer({
name: "weather",
version: "1.0.0",
});
// Register weather tools
server.registerTool(
"get_alerts",
{
description: "Get weather alerts for a state",
inputSchema: {
state: z
.string()
.length(2)
.describe("Two-letter state code (e.g. CA, NY)"),
},
},
async ({ state }) => {
const stateCode = state.toUpperCase();
const alertsUrl = `${NWS_API_BASE}/alerts?area=${stateCode}`;
const alertsData = await makeNWSRequest<AlertsResponse>(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.registerTool(
"get_forecast",
{
description: "Get weather forecast for a location",
inputSchema: {
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<PointsResponse>(pointsUrl);
if (!pointsData) {
return {
content: [
{
type: "text",
text: `Failed to retrieve grid point data for coordinates: ${latitude}, ${longitude}. This location may not be supported by the NWS API (only US locations are supported).`,
},
],
};
}
const forecastUrl = pointsData.properties?.forecast;
if (!forecastUrl) {
return {
content: [
{
type: "text",
text: "Failed to get forecast URL from grid point data",
},
],
};
}
// Get forecast data
const forecastData = await makeNWSRequest<ForecastResponse>(forecastUrl);
if (!forecastData) {
return {
content: [
{
type: "text",
text: "Failed to retrieve forecast data",
},
],
};
}
const periods = forecastData.properties?.periods || [];
if (periods.length === 0) {
return {
content: [
{
type: "text",
text: "No forecast periods available",
},
],
};
}
// Format forecast periods
const formattedForecast = periods.map((period: ForecastPeriod) =>
[
`${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,
},
],
};
},
);
return server;
}
// Stdio transport mode (default, for local use)
async function runStdioMode() {
const server = createServer();
const transport = new StdioServerTransport();
await server.connect(transport);
console.error("Weather MCP Server running on stdio");
}
// HTTP/SSE transport mode (for remote access)
async function runHttpMode() {
const PORT = process.env.PORT ? parseInt(process.env.PORT, 10) : 3000;
const app = express();
app.use(express.json());
// Map to store transports by session ID
const transports: Record<string, StreamableHTTPServerTransport> = {};
// POST endpoint for MCP requests
app.post("/mcp", async (req, res) => {
const sessionId = req.headers["mcp-session-id"] as string | undefined;
if (sessionId) {
console.log(`Received MCP request for session: ${sessionId}`);
} else {
console.log("New MCP request (no session ID)");
}
try {
let transport: StreamableHTTPServerTransport;
if (sessionId && transports[sessionId]) {
// Reuse existing transport for this session
transport = transports[sessionId];
} else if (!sessionId && isInitializeRequest(req.body)) {
// New initialization request - create new transport
transport = new StreamableHTTPServerTransport({
sessionIdGenerator: () => randomUUID(),
onsessioninitialized: (newSessionId) => {
console.log(`Session initialized with ID: ${newSessionId}`);
transports[newSessionId] = transport;
},
});
// Set up cleanup on close
transport.onclose = () => {
const sid = transport.sessionId;
if (sid && transports[sid]) {
console.log(`Transport closed for session ${sid}`);
delete transports[sid];
}
};
// Connect server to transport
const server = createServer();
await server.connect(transport);
await transport.handleRequest(req, res, req.body);
return;
} else {
// Invalid request
res.status(400).json({
jsonrpc: "2.0",
error: {
code: -32000,
message: "Bad Request: No valid session ID provided",
},
id: null,
});
return;
}
// Handle request with existing transport
await transport.handleRequest(req, res, req.body);
} catch (error) {
console.error("Error handling MCP request:", error);
if (!res.headersSent) {
res.status(500).json({
jsonrpc: "2.0",
error: {
code: -32603,
message: "Internal server error",
},
id: null,
});
}
}
});
// GET endpoint for SSE streams
app.get("/mcp", async (req, res) => {
const sessionId = req.headers["mcp-session-id"] as string | undefined;
if (!sessionId || !transports[sessionId]) {
res.status(400).send("Invalid or missing session ID");
return;
}
const lastEventId = req.headers["last-event-id"];
if (lastEventId) {
console.log(`Client reconnecting with Last-Event-ID: ${lastEventId}`);
} else {
console.log(`Establishing new SSE stream for session ${sessionId}`);
}
const transport = transports[sessionId];
await transport.handleRequest(req, res);
});
// DELETE endpoint for session termination
app.delete("/mcp", async (req, res) => {
const sessionId = req.headers["mcp-session-id"] as string | undefined;
if (!sessionId || !transports[sessionId]) {
res.status(400).send("Invalid or missing session ID");
return;
}
console.log(`Received session termination request for session ${sessionId}`);
try {
const transport = transports[sessionId];
await transport.handleRequest(req, res);
} catch (error) {
console.error("Error handling session termination:", error);
if (!res.headersSent) {
res.status(500).send("Error processing session termination");
}
}
});
// Start HTTP server
app.listen(PORT, () => {
console.log(`Weather MCP Server listening on port ${PORT}`);
console.log(`Endpoint: http://localhost:${PORT}/mcp`);
});
// Handle graceful shutdown
process.on("SIGINT", async () => {
console.log("\nShutting down server...");
// Close all active transports
for (const sessionId in transports) {
try {
console.log(`Closing transport for session ${sessionId}`);
await transports[sessionId].close();
delete transports[sessionId];
} catch (error) {
console.error(`Error closing transport for session ${sessionId}:`, error);
}
}
console.log("Server shutdown complete");
process.exit(0);
});
}
// Main entry point
async function main() {
const transportMode = process.env.TRANSPORT || "stdio";
if (transportMode === "http") {
await runHttpMode();
} else {
await runStdioMode();
}
}
main().catch((error) => {
console.error("Fatal error in main():", error);
process.exit(1);
});
