Developing Model Context Protocol servers becomes much easier with proper testing tools. The MCP Inspector provides a straightforward interface to test and validate your implementations during development.
What is the MCP Inspector?
The MCP Inspector is a specialized development tool for working with MCP servers that offers:
- Visual interface for MCP connections
- Real-time request/response monitoring
- Capability testing and validation
- Support for authenticated connections
Using the Inspector
The simplest way to use the inspector is with npx:
This starts:
- The inspector UI (default port 6274)
- An MCP proxy server (default port 6277)
For standard usage:
Open the UI in your browser to start inspecting your server.
Testing with the Inspector
The inspector helps you validate your MCP server implementation:
- Connection Testing: Verify your server establishes connections correctly
- Capability Validation: Check that your server implements required endpoints
- Request/Response Inspection: Monitor full data exchange
- Authentication Testing: Validate secure connections with bearer tokens
Best Practices
For effective MCP development with the Inspector:
- Test capabilities one at a time for easier debugging
- Use the inspector to verify error handling works correctly
- Monitor response times for performance testing
- Add the inspector to your development workflow
For comprehensive debugging techniques beyond the inspector, see the Debugging Guide.
Advanced Usage
The inspector supports several configuration options:
| Setting | Description | Default |
|---|---|---|
| MCP_SERVER_REQUEST_TIMEOUT | Request timeout (ms) | 10000 |
| MCP_REQUEST_TIMEOUT_RESET_ON_PROGRESS | Reset timeout on progress | true |
| MCP_REQUEST_MAX_TOTAL_TIMEOUT | Maximum total timeout (ms) | 60000 |
These can be adjusted through the UI and persist across sessions.
Security Considerations
Keep these security aspects in mind:
- The proxy server has permissions to spawn local processes
- Use it only in development environments, not production
- Don't expose the proxy to untrusted networks
Resources
The MCP Inspector is continuously evolving to help developers build robust, compliant, and reliable MCP servers.