server

mcpServer.ts

import express from "npm:express";
import { randomUUID } from "node:crypto";
import { McpServer } from "npm:@modelcontextprotocol/sdk/server/mcp.js";
import { StreamableHTTPServerTransport } from "npm:@modelcontextprotocol/sdk/server/streamableHttp.js";
import { z } from "npm:zod";

const PORT = 3000;
const MCP_ENDPOINT = "/mcp";

const app = express();
app.use(express.json());

const server = new McpServer({
  name: "Calculator Server",
  version: "1.0.0",
});

server.tool(
  "add",
  {
    a: z.number().describe("First number to add"),
    b: z.number().describe("Second number to add"),
  },
  async ({ a, b }) => {
    console.log(`Adding ${a} and ${b}`);
    return {
      content: [{ type: "text", text: `The result is ${a + b}` }],
    };
  },
);

const transport = new StreamableHTTPServerTransport({
  sessionIdGenerator: () => randomUUID(),
  onsessioninitialized: (sid) => {
    console.log(`Session initialized: ${sid}`);
  },
});

await server.connect(transport);
console.log("MCP Server connected to transport");

async function handleRequest(req, res) {
  console.log(`Handling MCP request`);
  console.log(`Request body:`, JSON.stringify(req.body, null, 2));

  try {
    await transport.handleRequest(req, res, req.body);
  } catch (error) {
    console.error('Error handling MCP request:', error);
    res.status(500).json({
      jsonrpc: "2.0",
      error: {
        code: -32603,
        message: "Internal error: " + error.message,
      },
      id: req.body?.id || null,
    });
  }
}

app.post(MCP_ENDPOINT, handleRequest);
app.get(MCP_ENDPOINT, handleRequest);
app.delete(MCP_ENDPOINT, handleRequest);

app.listen(PORT, () => {
  console.log(`MCP Server listening on port ${PORT}`);
});