Calculator MCP Server

A small Model Context Protocol (MCP) server that exposes basic calculator operations over stdio.

Features

The server provides these tools:

All arguments must be numbers. div returns an error when op2 is 0.

Related MCP server: Math MCP Server

Requirements

• Node.js 18 or later

• npm

Setup

Install the dependencies from this directory:

npm install

Run the server

Start the MCP server over stdio:

npm start

The server waits for an MCP client to connect, so it does not print normal application output to the terminal.

Test with the example client

The example client starts the server, lists its tools, and calls div with 10 and 0 to demonstrate the division-by-zero error:

npm run test-client

To test a successful operation, update the callTool arguments in mcp-client-test.ts, for example:

arguments: { op1: 10, op2: 2 },

Use MCP Inspector

Run the interactive MCP Inspector with:

npm run mcp-inspect

Open the URL printed by the command, then select a calculator tool and provide values for op1 and op2.

Project files

• mcp-server.ts - MCP server and calculator tool definitions

• mcp-client-test.ts - example MCP client

• mcp-calculator.gif - tutorial walkthrough

• package.json - scripts and dependencies