# Calculator Tool
## Description
The `calculator` tool is a Go-based gRPC service that evaluates mathematical expressions from a string. It leverages the `govaluate` library to support basic arithmetic operations (`+`, `-`, `*`, `/`), parentheses for order of operations, and many other common mathematical functions.
## Parameters
The tool accepts a single argument in a JSON object:
| Parameter | Type | Required | Description |
|--------------|----------|----------|----------------------------------------------------------------|
| `expression` | `string` | **Yes** | The mathematical expression to evaluate (e.g., `"(2 + 2) * 4"`). |
## Response
* **Successful Calculation:** If the expression is valid, the tool returns the resulting number.
* **Error:** If the expression is malformed or contains an error during evaluation, the tool returns an error message.
## Usage Example
Here is an example of how to use the `calculator` tool to evaluate a complex expression. This example uses `curl` to interact with the MCP server's HTTP/REST gateway.
**Request:**
```bash
curl -X POST http://localhost:8002/v1/tools:run \
-d '{
"name": "calculator",
"arguments": {
"expression": "(12.5 + 7.5) * (10 / 2)"
}
}'
```
**Successful Response:**
```json
{
"result": {
"numberValue": 100
}
}
```
## Configuration
The tool's configuration is managed through a `config.json` file located in the tool's directory.
**Example `config.json`:**
```json
{
"port": 50052,
"command": ["go", "run", "."]
}
```
* `port`: The port on which the tool's gRPC server will listen.
* `command`: The command and arguments to execute the tool.
## Health and Logging
* **Health Checks:** This tool implements the standard gRPC Health Checking Protocol. The main MCP server will not route requests to it if it is unhealthy.
* **Logging:** The tool uses a structured JSON logger (`slog`) to log all operations to standard output.
## Testing
To test the Calculator tool, you can run the provided integration tests. These tests cover various expressions and edge cases. Navigate to the tool's directory and run:
```bash
go test ./...
```
