MCP Debugger

The MCP Debugger is an interactive client for Model Context Protocol servers. Where MCP Servers manages the server processes Claude Code uses, the MCP Debugger lets you connect to any MCP server, exercise its tools and resources, work through authentication, and watch the raw protocol traffic — invaluable when building or troubleshooting a server.

Opening the Debugger

Click MCP Debugger in the sidebar, jump to it from the Quick Swap menu, or go to /mcp-tester directly.

Connections & Folders

The left rail lists your saved connections. Click + New to add one. Give each connection a Name and, optionally, a Folder (for example Production, Local, or a customer name) to group the list.

Transports

Each connection uses one of three transports:

  • stdio (local subprocess) — Launch a local server as a child process. Provide a Command, Arguments (one per line), and optional Environment variables (KEY=VALUE per line).
  • http (Streamable HTTP) — The modern single-endpoint HTTP transport. Point it at the endpoint the server accepts MCP messages on (often /mcp or /).
  • sse (legacy HTTP+SSE) — The legacy event-stream transport, where the server announces its POST endpoint over an SSE stream.

Authentication

HTTP and SSE connections support three auth modes:

  • None
  • Bearer — A token added as an Authorization: Bearer … header.
  • OAuth — A full OAuth 2.1 authorization-code flow.

OAuth Flow

  1. Save the connection with OAuth selected.
  2. Click Discover to run the discovery chain and locate the server’s authorization and token endpoints. If discovery fails over http://, ClawIDE automatically retries over https:// and adopts the secure URL.
  3. Click Authorize to open the provider’s login in a popup. ClawIDE handles dynamic client registration, PKCE, and resource indicators automatically.
  4. On success, the connection shows an authorized badge. Tokens that expire show token expired; use Clear token to remove stored credentials.

If a server doesn’t advertise its endpoints, switch on Manual setup to enter the authorization endpoint, token endpoint, client ID/secret, and scopes by hand.

Inspecting a Server

Once connected, a set of tabs becomes available:

  • Overview — Server info, advertised capabilities, and OAuth controls.
  • Tools — Browse the server’s tools, inspect each tool’s input schema, fill in an arguments form, and Run it to see the result.
  • Resources — List resources and Read any resource by URI (you can type a custom URI).
  • Prompts — Browse the server’s prompts and expand each one’s argument schema.
  • Trace — A live JSON-RPC trace (over SSE) showing every message in and out, plus stderr, OAuth, and transport events. Clear it any time.
  • Diagnostics — Plain-language remediation guides keyed to the error codes ClawIDE surfaces.

Health Checks

Each connection row shows a colored health dot. Click the heartbeat icon on a row to check a single server, or Check all in the Connections header to check every one. A reachable server reports its round-trip latency and server name; an unreachable one reports the error.

Storage

Connections are saved to ~/.clawide/mcp-tester/connections.json. OAuth tokens are kept separately in ~/.clawide/mcp-tester/tokens.json with owner-only (0600) permissions so secrets stay local to your machine.