Calculator MCP Server

A simple Model Context Protocol (MCP) server built in Node.js that provides some basic arithmetic calculation tools.The srver uses official MCP JavaScript SDK, Zod for input validation and Standard Input/Output (stdio to communicate with MCP clients.

Features:

• Addition of two numbers

• Subtraction of one number from another

• Multiplication of two numbers

• Division of a number by another number with handling of divide by zero error

• Percentage calculation

Technologies used:

• JavaScript ES Module

• Node.js

• Model Context Protocol (MCP)

• MCP JavaScript SDK

• Zod

Tools Available:

Note Add, Subtract, Multiply and Divide take a and b as input, while Percentage takes Value and Percent as inputs.

Project Folder Structure:

calculator-mcp-server
├── src
│   ├── server
│   │   └── calculatorServer.js
│   ├── tools
│   │   ├── addition.js
│   │   ├── division.js
│   │   ├── multiplication.js
│   │   ├── percentage.js
│   │   └── subtraction.js
│   └── index.js
├── .gitignore
├── LICENSE
├── README.md
├── package-lock.json
└── package.json

Prerequisites:

1. Node.js Version: v24.11.1

2. npm Version: v11.6.2

Install dependencies:

Clone repository using https://github.com/sdewanshu-lab/calculator-mcp-server.git

1. npm install

Run Server:

1. npm run start

Testing:

Launch MCP Inspector via npx @modelcontextprotocol/inspector This will open MCP Inspector in browser or give an URL. Copy that URL and paste it in browser.

Server Settings:

Note After configuring the server, connect it and open Tools. Select the desired tool from the list and perform the calculations. Examples are provided in Tools Available section.

GitHub Copilot Integration (VS Code)

The Calculator MCP Server can be connected to GitHub Copilot Chat in VS Code using stdio transport.

The prerequisites are:

• Node.js and npm

• Visual Studio Code with MCP support

• GitHub Copilot Chat access

• Dependencies installed using npm

Configuration

Create .vscode/mcp.js file in project root folder

zuse the code:

    {
    "servers":{
        "calculator-mcp":{
            "type":"stdio",
            "command":"node",
            "args":[
                "src/index.js"
            ]
        }
    }
}

Open the project folder in VS Code. Start calculator-mcp from the MCP configuration controls or the MCP: List Servers command. Confirm the server is running.

Testing with Copilot Chat

1. Open GitHub Copilot Chat in Agent mode.

2. Ensure the calculator MCP tools are enabled and available.

3. Ask Copilot to invoke a calculator tool.

4. Review the tool invocation and result.

Example prompts:

• Use the Add tool from my calculator-mcp MCP server to calculate 125 + 375. Expected result: 500.

• Calculate 35% of 1,200 using my calculator MCP server. Choose the appropriate tool yourself. Expected result: 420.

• Using my calculator MCP server, calculate 25% of 840 and then add 150 to that result. Expected result: 360, using Percentage and Add.

Validation

All five calculator tools were tested with MCP Inspector and GitHub Copilot Chat. Tests included division-by-zero handling, automatic tool selection, and sequential tool invocation.

Note: GitHub Copilot Chat access and usage limits depend on the user's GitHub account and plan. No separate npm start command is needed when VS Code launches the server through the MCP configuration.

Version

1.0.0

More functionalities are yet to be added and new versions are to be released.

Author

Dewanshu Sharma