MCP Inspector
Official debugging and testing tool for Model Context Protocol servers, providing a web interface to inspect server capabilities, test tools, and debug MCP implementations.
MCP Inspector
The MCP Inspector is the official debugging and development tool for Model Context Protocol servers, available as an npm package at @modelcontextprotocol/inspector. It provides a comprehensive web-based interface for testing, debugging, and exploring MCP server implementations.
Installation & Usage
# Install globally
npm install -g @modelcontextprotocol/inspector
# Run inspector
npx @modelcontextprotocol/inspector
The inspector typically runs on port 6277 by default and opens automatically in your browser at http://localhost:6277.
Core Features
| Feature | Purpose |
|---|---|
| Server Connection | Connect to any MCP server via stdio, SSE, or WebSocket |
| Tool Testing | Interactive interface to call and test server tools |
| Resource Browser | Explore available resources and their content |
| Schema Validation | Verify server responses match MCP protocol |
| Real-time Debugging | Monitor message flow between client and server |
What You Can Inspect
Server Capabilities
- Available tools and their schemas
- Resource listings and metadata
- Supported prompts and templates
- Server initialization parameters
Tool Testing
- Execute tools with custom parameters
- View response data and error handling
- Test edge cases and validation
- Measure performance and response times
Protocol Compliance
- Validate message formats
- Check schema adherence
- Monitor transport layer behavior
- Debug connection issues
Development Workflow
- Start Your Server: Launch your MCP server implementation
- Run Inspector: Execute
npx @modelcontextprotocol/inspector - Connect: Point inspector to your server (usually stdio transport)
- Explore: Browse tools, resources, and capabilities
- Test: Execute tools with various inputs
- Debug: Identify and fix protocol or implementation issues
Common Use Cases
- Server Development: Test new MCP server implementations
- Integration Testing: Verify server behavior before deployment
- Protocol Learning: Understand MCP message flow and structure
- Debugging: Diagnose connection or response issues
- Documentation: Generate examples of tool usage and responses
Configuration Options
The inspector can be configured for different server types:
# Connect to stdio server
npx @modelcontextprotocol/inspector --transport stdio --command "node server.js"
# Connect to SSE server
npx @modelcontextprotocol/inspector --transport sse --url "http://localhost:3000/sse"
# Specify custom port
npx @modelcontextprotocol/inspector --port 8080
The MCP Inspector is an essential tool for anyone developing or working with MCP servers, providing the visibility and testing capabilities needed to build robust integrations.