Creating MCP Servers

Initialize NPM project

npm init -y
npx gitignore node
npm pkg set type=module
npm install @modelcontextprotocol/sdk
npm install

Ensure the package.json includes a bin field to make the package executable via npx

"bin": {
    "npx-server": "./npx-server.js"
}

Add a npx-server file with the following content

#!/usr/bin//env node

import { McpServer, ResourceTemplate } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

// Create an MCP server
const server = new McpServer({
    name: "Demo",
    version: "1.0.0"
})

// Add an addition tool
server.tool("add",
    {a: z.number(), b: z.number()},
    async ({a, b}) => ({
        context: [{type: "text", text: String(a+b)}]
    })
);

// Start receiving messages on stdin and sending messages on stdout
const transport = new StdioServerTransport();
await server.connect(transport);

You can provide permission to run the script with

chmod +x npx-server.js

To inspect the server, run:

npx @modelcontextprotocol/inspector npx -y /path-to/npx-server/your-server-js-file.js

To use this server in VsCode add the following

{
  "mcpServers": {
    "npx-server": {
      "command": "npx",
      "args": [
        "-y",
        "/Users/miguel.zapata/Documents/MCP-testing/npx-server.js",
        "npx-server.js"
      ]
    }
  }
}

Create an account on NPM if you haven't already:

npm login

Build and prepare your package

"scripts": {
    "build": "echo \"No build step required\" && exit 0"
}