# 🧮 Testing the MCP Calculator Tool in VS Code
This guide will help you test the MCP (Model Context Protocol) calculator tool in VS Code using the built-in demo client.
## 📋 Prerequisites
Before testing, ensure you have:
- ✅ Node.js installed (v16 or later)
- ✅ VS Code with this workspace open
- ✅ TypeScript compiled (the `dist/` folder should exist)
## 🚀 Quick Start
### 1. Open VS Code Terminal
In VS Code, open the integrated terminal:
- Press `Ctrl + `` (backtick) or
- Go to **Terminal** → **New Terminal**
### 2. Navigate to Project Directory
```powershell
cd "c:\CDrive\Workshops\CustomAI\mcpstdio\hjmcpstdio"
```
### 3. Build the Project (if needed)
```powershell
npm run build
```
### 4. Run the Calculator Demo
```powershell
node dist/calculator-demo.js
```
## 📊 Expected Output
When you run the demo, you should see output similar to this:
```
🚀 Starting MCP Server for Calculator Demo...
🔧 Server: MCP Stdio Server running...
📡 Initializing connection...
✅ Initialization successful
🔧 Server capabilities: {
"resources": {},
"tools": {},
"prompts": {}
}
📋 Listing available tools...
🛠️ Available tools:
• calculate: Perform mathematical calculations
• list_files: List files in the project directory
🧮 Calculating: 2 + 3
📊 Result: Calculation: 2 + 3 = 5
🧮 Calculating: 10 * 5
📊 Result: Calculation: 10 * 5 = 50
🧮 Calculating: (15 + 5) / 4
📊 Result: Calculation: (15 + 5) / 4 = 5
🧮 Calculating: 2.5 * 3.14159
📊 Result: Calculation: 2.5 * 3.14159 = 7.853975
🧮 Calculating: 100 - 25 + 10
📊 Result: Calculation: 100 - 25 + 10 = 85
🧮 Calculating: Math.sqrt(16)
📊 Result: Error calculating expression: Unexpected token '.'
🧮 Calculating: 2**8
📊 Result: Calculation: 2**8 = 256
🔚 Stopping server...
✅ Demo completed
```
## 🛠️ Manual Testing with Individual Calculations
### Option 1: Modify the Demo Script
You can edit `src/calculator-demo.ts` to test your own expressions:
1. Open `src/calculator-demo.ts` in VS Code
2. Find the `expressions` array around line 140
3. Replace or add your own mathematical expressions:
```typescript
const expressions = [
"5 * 5", // Your custom calculation
"100 / 4", // Another custom calculation
"(10 + 5) * 2", // Complex expression
];
```
4. Rebuild and run:
```powershell
npm run build
node dist/calculator-demo.js
```
### Option 2: Create a Simple Test Script
Create a new file `test-calc.js` in the project root:
```javascript
const { spawn } = require('child_process');
async function testCalculation(expression) {
const server = spawn('node', ['dist/server.js'], {
stdio: ['pipe', 'pipe', 'pipe']
});
const initMsg = JSON.stringify({
jsonrpc: "2.0",
id: 1,
method: "initialize",
params: {
protocolVersion: "2024-11-05",
capabilities: {},
clientInfo: { name: "test", version: "1.0.0" }
}
}) + '\n';
const calcMsg = JSON.stringify({
jsonrpc: "2.0",
id: 2,
method: "tools/call",
params: {
name: "calculate",
arguments: { expression }
}
}) + '\n';
server.stdin.write(initMsg);
setTimeout(() => server.stdin.write(calcMsg), 100);
server.stdout.on('data', (data) => {
const lines = data.toString().split('\n');
lines.forEach(line => {
if (line.trim()) {
try {
const response = JSON.parse(line);
if (response.id === 2 && response.result?.content) {
console.log(`${expression} = ${response.result.content[0].text.split(' = ')[1]}`);
server.kill();
}
} catch (e) {}
}
});
});
}
// Test a calculation
testCalculation(process.argv[2] || "2 + 2");
```
Then run: `node test-calc.js "15 * 3"`
## 🔧 Using VS Code MCP Extension
If you have the MCP extension installed in VS Code:
### 1. Configure MCP in VS Code
Ensure your `mcp.json` file is properly configured:
```json
{
"mcpServers": {
"hjmcp-stdio": {
"command": "node",
"args": ["dist/server.js"],
"cwd": "C:/CDrive/Workshops/CustomAI/mcpstdio/hjmcpstdio",
"transport": "stdio"
}
}
}
```
### 2. Access Calculator via MCP
1. Open the Command Palette (`Ctrl+Shift+P`)
2. Look for MCP-related commands
3. Connect to your `hjmcp-stdio` server
4. Use the calculator tool through the MCP interface
## 🧪 What the Calculator Can Do
### ✅ Supported Operations
- **Basic arithmetic**: `+`, `-`, `*`, `/`
- **Parentheses**: `(`, `)`
- **Exponentiation**: `**` (e.g., `2**8 = 256`)
- **Decimal numbers**: `2.5 * 3.14159`
- **Complex expressions**: `(15 + 5) / 4 * 2`
### ❌ Security Limitations (By Design)
- **Function calls**: `Math.sqrt(16)` ❌
- **Variables**: `x = 5` ❌
- **Code execution**: Any non-mathematical code ❌
The calculator sanitizes input to prevent code injection while allowing safe mathematical expressions.
## 🐛 Troubleshooting
### Error: "Cannot find module"
```powershell
npm install
npm run build
```
### Error: "Server not responding"
- Check that the `dist/` folder exists
- Ensure TypeScript compilation was successful
- Verify Node.js version (should be v16+)
### Error: "Permission denied"
- Run VS Code as administrator if needed
- Check file permissions in the project directory
### Calculator returns errors
- Ensure expressions only contain numbers and basic operators
- Avoid spaces in decimal numbers (`2.5` not `2 .5`)
- Use parentheses for complex expressions
## 📚 Next Steps
- **Extend the calculator**: Add more mathematical functions
- **Create new tools**: Add tools for file operations, data processing, etc.
- **Integration**: Connect your MCP server to other applications
- **Documentation**: Explore the MCP protocol specification
## 🎯 Key Files
- `src/server.ts` - Main MCP server implementation
- `src/calculator-demo.ts` - Demo client for testing
- `dist/server.js` - Compiled server (auto-generated)
- `mcp.json` - VS Code MCP configuration
- `package.json` - Node.js dependencies and scripts
Happy calculating! 🧮✨
