How do I use MCP Calculation Server?

1. Click on "Install Server". 2. Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state. 3. In the chat, type @ followed by the MCP server name and your instructions, e.g., "@MCP Calculation Server What's 144 divided by 12?" That's it! The server will respond to your query, and you can continue using it as needed. Here is a step-by-step guide with screenshots.

MCP — Calculation Server

A stateless Model Context Protocol (MCP) server that exposes arithmetic tools over HTTP. MCP clients (Claude Desktop, VS Code Copilot, Cursor, etc.) can connect to it and invoke the tools conversationally.

Architecture

MCP Client (Claude, VS Code, etc.)
        │
        │  HTTP POST /mcp  (JSON-RPC 2.0)
        ▼
  Express.js server  :3000
        │
        │  per-request lifecycle
        ▼
  McpServer  ──  StreamableHTTPServerTransport
        │
  4 calculation tools

Each incoming request gets a fresh McpServer instance that is torn down when the response closes (stateless mode).

Related MCP server: MCP Calculator Streamable HTTP

Tools

Tool	Description	Inputs	Output
`add_two_numbers`	Add two numbers	`a: number`, `b: number`	`result: number`
`subtract_two_numbers`	Subtract the second number from the first	`a: number`, `b: number`	`result: number`
`multiply_two_numbers`	Multiply two numbers	`a: number`, `b: number`	`result: number`
`divide_two_numbers`	Divide the first number by the second	`a: number`, `b: number`	`result: number`

divide_two_numbers returns an error response when b is 0 rather than throwing.

Prerequisites

Node.js 18+
npm

Getting Started

1. Install dependencies

npm install

2. Run in development mode (hot reload)

npm run dev

The server starts at http://localhost:3000/mcp.

3. Build for production

Note: tsconfig.json compiles to ./build/, but package.json's start script points to dist/index.js. Fix one of them before running production mode.

# Option A — update start script to match tsconfig outDir
npm run build
node build/index.js

# Option B — update tsconfig outDir to "dist" and then run
npm run build
npm start

4. Run with Docker

docker build -t mcp-calculation .
docker run -p 3000:3000 mcp-calculation

Custom port:

docker run -p 8080:8080 -e PORT=8080 mcp-calculation

Connecting an MCP Client

VS Code (Copilot / Claude extension)

A .vscode/mcp.json is already included:

{
  "servers": {
    "my-mcp-server-de2625e8": {
      "url": "http://localhost:3000/mcp",
      "type": "http"
    }
  }
}

Start the server (npm run dev), then open the MCP panel in VS Code — the Calculation Server will appear automatically.

Claude Desktop

Add the following to your Claude Desktop config (claude_desktop_config.json):

{
  "mcpServers": {
    "calculation-server": {
      "url": "http://localhost:3000/mcp",
      "type": "http"
    }
  }
}

Any HTTP MCP client

Setting	Value
URL	`http://localhost:3000/mcp`
Transport	HTTP (Streamable HTTP)
Method	`POST`
Protocol	JSON-RPC 2.0

Using the Tools

Once connected, ask your MCP client naturally:

What is 42 plus 58?
What is 100 divided by 4?
Multiply 7 by 8.
Subtract 15 from 100.

Direct HTTP example (curl)

# List available tools
curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/list"
  }'

# Call add_two_numbers
curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 2,
    "method": "tools/call",
    "params": {
      "name": "add_two_numbers",
      "arguments": { "a": 12, "b": 30 }
    }
  }'

Expected response:

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "content": [{ "type": "text", "text": "The sum of 12 and 30 is 42" }],
    "structuredContent": { "result": 42 }
  }
}

# Division by zero — returns an error response (not an HTTP error)
curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 3,
    "method": "tools/call",
    "params": {
      "name": "divide_two_numbers",
      "arguments": { "a": 10, "b": 0 }
    }
  }'

Environment Variables

Variable	Default	Description
`PORT`	`3000`	Port the HTTP server listens on

Project Structure

mcp-calculation/
├── src/
│   └── index.ts        # Server entry point — tools + Express setup
├── .vscode/
│   └── mcp.json        # VS Code MCP client config
├── Dockerfile
├── package.json
└── tsconfig.json

Tech Stack

Package	Purpose
`@modelcontextprotocol/sdk`	MCP server + transport primitives
`express`	HTTP server (v5)
`zod`	Input/output schema validation
`tsx`	TypeScript execution for dev mode
`typescript`	Type checking + build

MCP Calculation Server