# MCP Inspector Guide for LLMs
This guide provides detailed information about using the MCP Inspector tool for testing, debugging, and validating MCP servers.
## 1. Getting Started
### Installation and Basic Usage
```bash
# Run directly without installation
npx mcp-inspector <server-command>
# For NPM/PyPi packages
npx mcp-inspector npx -y @your-package/server-name
# For local development
npx mcp-inspector node path/to/your/server.js
npx mcp-inspector python path/to/your/server.py
```
### Server Connection Setup
1. Select appropriate transport (stdio/SSE)
2. Configure command-line arguments
3. Set required environment variables
4. Test initial connection
## 2. Core Features
### Server Connection Pane
1. Transport Selection:
- stdio for local servers
- SSE for network-based servers
- Custom transport configuration
2. Connection Settings:
- Command-line arguments
- Environment variables
- Connection timeouts
3. Status Monitoring:
- Connection state
- Protocol version
- Capability negotiation
### Resources Tab
1. Resource Listing:
```typescript
// Example resource listing structure
{
resources: [
{
uri: "custom://resource",
name: "Resource Name",
description: "Resource description",
mimeType: "text/plain"
}
]
}
```
2. Resource Inspection:
- View metadata
- Examine content
- Check MIME types
- Test resource reading
3. Subscription Testing:
- Subscribe to updates
- Monitor changes
- Test unsubscribe
### Prompts Tab
1. Template Inspection:
```typescript
// Example prompt structure
{
name: "prompt-name",
description: "Prompt description",
arguments: [
{
name: "arg1",
description: "Argument description",
required: true
}
]
}
```
2. Testing Features:
- View available templates
- Test with custom arguments
- Preview generated messages
- Validate responses
### Tools Tab
1. Tool Discovery:
```typescript
// Example tool listing
{
tools: [
{
name: "tool-name",
description: "Tool description",
inputSchema: {
type: "object",
properties: {
// Parameter definitions
}
}
}
]
}
```
2. Testing Features:
- List available tools
- Validate schemas
- Test execution
- Monitor results
### Notifications Pane
1. Message Types:
- Server logs
- Error messages
- Status updates
- Progress notifications
2. Monitoring:
- Real-time updates
- Message filtering
- Error tracking
## 3. Testing Workflows
### Development Workflow
1. Initial Testing:
```bash
# Start Inspector with development server
npx mcp-inspector npm run dev
```
2. Development Cycle:
- Make code changes
- Restart server
- Test affected features
- Monitor logs
- Debug issues
3. Feature Testing:
- Verify basic functionality
- Test edge cases
- Check error handling
- Validate responses
### Resource Testing
1. Listing Verification:
- Check resource discovery
- Validate metadata
- Test pagination
- Check updates
2. Content Testing:
- Read resource content
- Verify MIME types
- Test binary data
- Check encoding
3. Subscription Testing:
- Subscribe to resources
- Monitor updates
- Test unsubscribe
- Verify notifications
### Tool Testing
1. Discovery Testing:
- List available tools
- Verify schemas
- Check descriptions
- Validate metadata
2. Execution Testing:
- Test with valid inputs
- Try invalid inputs
- Check error handling
- Monitor progress
- Validate results
### Prompt Testing
1. Template Verification:
- Check available prompts
- Validate arguments
- Test descriptions
- Verify schemas
2. Generation Testing:
- Test with arguments
- Check message format
- Validate content
- Test error cases
## 4. Debugging
### Common Issues
1. Connection Problems:
- Check server process
- Verify transport
- Monitor initialization
- Check capabilities
2. Message Errors:
- Validate formats
- Check handlers
- Monitor responses
- Track errors
3. Resource Issues:
- Check permissions
- Verify paths
- Test content types
- Monitor updates
### Debugging Tools
1. Console Logging:
```typescript
// Server-side logging
console.error("Debug message");
```
2. Message Inspection:
- View raw messages
- Check formatting
- Track request/response
- Monitor timing
3. Error Analysis:
- Stack traces
- Error codes
- Response validation
- Context examination
## 5. Best Practices
### Testing Strategy
1. Systematic Approach:
- Test core features first
- Add edge cases
- Verify error handling
- Check performance
2. Resource Management:
- Monitor memory usage
- Check file handles
- Verify cleanup
- Test limits
3. Error Handling:
- Test all error paths
- Verify messages
- Check recovery
- Monitor cleanup
### Security Testing
1. Input Validation:
- Test boundaries
- Try invalid input
- Check sanitization
- Verify limits
2. Authentication:
- Test credentials
- Check permissions
- Verify tokens
- Monitor access
3. Resource Protection:
- Test access control
- Check paths
- Verify isolation
- Monitor usage
## 6. Performance Testing
### Response Time
1. Operation Timing:
- Track latency
- Monitor variance
- Check thresholds
- Log outliers
2. Batch Operations:
- Test concurrent requests
- Monitor memory
- Check throughput
- Verify ordering
### Resource Usage
1. Memory Monitoring:
- Track allocation
- Check leaks
- Monitor peaks
- Verify cleanup
2. Connection Management:
- Test connection stability
- Check timeouts
- Monitor states
- Verify cleanup
This guide should be used as a reference when testing and debugging MCP servers using the Inspector tool. Always consider the specific requirements of your server while following these guidelines.