🧮 MCP Calculator Server — Build Your First MCP Tool with TypeScript

A lightweight Model Context Protocol (MCP) server built in TypeScript using the official @modelcontextprotocol/sdk. This server exposes a simple tool that performs addition of two numbers, showcasing how to build custom MCP-compatible tools.

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🚀 Features

• Built using the official MCP SDK
• Implements a simple calculator with an add function
• Written in TypeScript
• Easy to extend for new MCP tools

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📁 Project Structure

my-calculator/
│
├── src/
│   └── index.ts          # Main server logic
├── package.json
├── tsconfig.json
└── README.md

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⚙️ Setup Instructions

1. Clone the Repository

git clone https://github.com/<your-username>/mcp-calculator-server.git
cd mcp-calculator-server

2. Install Dependencies

Make sure you have Node.js (v18+) and npm installed.

npm install

3. Build the Project

npm run build

4. Start the MCP Server

npm run start

You should see:

✅ MCP Calculator Server is running...

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🧠 How It Works

The project uses @modelcontextprotocol/sdk to create a minimal MCP server.

import { server } from "@modelcontextprotocol/sdk/server/stdio";
import { z } from "zod";

const s = server({
  name: "MCP Calculator Server",
});

s.tool(
  "add",
  {
    a: z.number(),
    b: z.number(),
  },
  async ({ a, b }) => ({
    content: [{ type: "text", text: `Result: ${a + b}` }],
  })
);

s.start();
console.log("✅ MCP Calculator Server is running...");

This registers an add tool, which takes two numbers (a, b) and returns their sum.

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🧩 Testing (Optional)

If you want to test manually:

npm run start

Then, you can connect this server to any MCP-compatible client (like Claude Desktop, ChatGPT with MCP, or other integrations).

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🧱 Build Commands Reference

Command	Description
npm run build	Compiles TypeScript into JavaScript
npm run start	Starts the MCP server with ts-node
npm install	Installs all dependencies

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🧰 Tech Stack

• TypeScript
• Node.js
• Model Context Protocol SDK
• Zod (Schema validation)

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📜 License

MIT License — feel free to fork and modify.