MCP Transport Debugger

How the Debugger Works

The debugger connects to your MCP server through a CORS proxy, performs the standard MCP handshake (initialize → notifications/initialized), then lets you send any JSON-RPC method with custom parameters. Every request and response is logged with timestamps and latency measurements, giving you a complete picture of the client-server communication.

Use Cases

• Testing new tools: After adding a tool to your MCP server, use the debugger to call tools/list and verify it appears, then send a tools/call request to test it works.
• Debugging errors: When Claude or Cursor reports a tool error, reproduce the exact call here to see the raw error response from your server.
• Performance monitoring: Each response shows latency in milliseconds. Identify slow tools before your users do.
• Protocol compliance: Verify your server responds correctly to all standard MCP methods — initialize, tools/list, resources/list, prompts/list.

Calling a Tool

To test a specific tool, use the custom request field with method tools/call and params:

{"name": "your_tool_name", "arguments": {"param1": "value1"}}

Requirements

• • Server must use Streamable HTTP or SSE transport
• • Server must be publicly accessible
• • stdio servers (local processes) cannot be debugged remotely

Related Tools