🧮 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.
🚀 Features
- Built using the official MCP SDK
- Implements a simple calculator with an
addfunction - Written in TypeScript
- Easy to extend for new MCP tools
📁 Project Structure
my-calculator/
│
├── src/
│ └── index.ts # Main server logic
├── package.json
├── tsconfig.json
└── README.md
⚙️ 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...
🧠 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.
🧩 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).
🧱 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 |
🧰 Tech Stack
- TypeScript
- Node.js
- Model Context Protocol SDK
- Zod (Schema validation)
📜 License
MIT License — feel free to fork and modify.