# MCP Arithmetic Server

A Model Context Protocol (MCP) server built with Node.js that exposes four arithmetic tools: `add`, `subtract`, `multiply`, and `divide`.

## Prerequisites

- Node.js 18+ (for top-level `await` and ES modules)

## Installation

```bash
npm install
```

## Running the server

```bash
npm start
```

The server communicates over **stdio**, so it can be connected to any MCP-compatible client.

## MCP Inspector

The [MCP Inspector](https://github.com/modelcontextprotocol/inspector) is a tool for inspecting and testing MCP servers. It provides a web UI where you can list tools and call them interactively.

```bash
npm run inspector
```

This launches the inspector in your browser. In the inspector UI:

- Set the **transport** to `Stdio`
- Set the **command** to `node` and the **args** to `server.js`
- Click **Connect**

You can then call any of the tools directly from the browser.

## Available tools

All four tools share the same input schema — two numbers:

| Property | Type   | Required | Description       |
| -------- | ------ | -------- | ----------------- |
| `a`      | number | yes      | The first number  |
| `b`      | number | yes      | The second number |

### `add`

Adds two numbers together.

```json
{ "a": 5, "b": 7 }
```

**Result:** `5 + 7 = 12`

### `subtract`

Subtracts the second number from the first (`a - b`).

```json
{ "a": 10, "b": 4 }
```

**Result:** `10 - 4 = 6`

### `multiply`

Multiplies two numbers together.

```json
{ "a": 5, "b": 7 }
```

**Result:** `5 * 7 = 35`

### `divide`

Divides the first number by the second (`a / b`). Returns an error if `b` is zero.

```json
{ "a": 15, "b": 3 }
```

**Result:** `15 / 3 = 5`

```json
{ "a": 15, "b": 0 }
```

**Result (error):** `Cannot divide by zero.`

## Testing locally

You can test the server with the MCP Inspector:

```bash
npm run server:inspect
```

## Connecting to a client

Configure your MCP client (e.g., Claude Desktop, VS Code Copilot) to use this command:

```
node D:\Learning_Projects\MCP\server.js
```