# Calculator Module Example
This is an example of a custom module for the MCP server. It adds a simple calculator tool that can perform basic arithmetic operations.
## Features
- Adds a calculator tool to the MCP server
- Supports basic arithmetic operations (add, subtract, multiply, divide)
- Demonstrates how to create a custom module with tools
## Installation
To use this module, copy the `custom-module` directory to the `src/modules` directory of your MCP server:
```bash
cp -r examples/custom-module src/modules/calculator
```
The module will be automatically loaded when the server starts.
## API Endpoints
| Endpoint | Method | Description |
|----------|--------|-------------|
| `/tools/calculator/info` | GET | Get information about the calculator tool |
| `/tools/calculator` | POST | Perform a calculation |
| `/modules/calculator` | GET | Get information about the calculator module |
## Usage Examples
### Get Calculator Tool Information
```javascript
fetch('http://localhost:3000/tools/calculator/info')
.then(response => response.json())
.then(data => console.log(data));
```
Response:
```json
{
"name": "calculator",
"description": "Performs basic arithmetic operations",
"parameters": {
"operation": {
"type": "string",
"description": "The operation to perform (add, subtract, multiply, divide)",
"required": true
},
"a": {
"type": "number",
"description": "The first operand",
"required": true
},
"b": {
"type": "number",
"description": "The second operand",
"required": true
}
}
}
```
### Perform a Calculation
```javascript
fetch('http://localhost:3000/tools/calculator', {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify({
operation: 'add',
a: 5,
b: 3
})
})
.then(response => response.json())
.then(data => console.log(data));
```
Response:
```json
{
"tool": "calculator",
"operation": "add",
"a": 5,
"b": 3,
"result": 8,
"timestamp": "2025-05-12T14:30:00Z"
}
```
## How It Works
The module exports three main components:
1. A `register` function that sets up the module's routes and functionality
2. An `unregister` function for cleanup (optional)
3. A `metadata` object with information about the module
When the MCP server starts, it calls the module's `register` function, passing in the Hono app instance. The module then registers its routes and functionality with the app.
The calculator tool is implemented as a simple function that takes an operation and two operands, performs the calculation, and returns the result.
