MCP failures are usually opaque from inside the client: a tool returns nothing, or the model quietly stops using it, and there is no obvious place to look. Putting a proxy between the two turns that into an ordinary debugging session — you can see the malformed argument, the error the server printed to stderr, and how long each call actually took.
A proxy and desktop UI for debugging MCP integrations. You either wrap a stdio server's launch command with `mcp-reticle run`, or point `mcp-reticle proxy` at an HTTP-based server, and everything crossing the wire becomes inspectable in real time.
- Raw JSON-RPC messages — requests, notifications and responses — with each request correlated to the response that answered it
- Latency and token estimates per exchange, so an expensive tool shows up as a number rather than a hunch
- Server stderr and crashes captured, instead of vanishing into the client's logs
- Session recording and log export
- Four entry points: `run` wraps a stdio server, `proxy` reverse-proxies an HTTP server, `ui` opens the desktop app, `daemon` runs a headless telemetry hub
- A log-only mode with `--log` when you want the capture without the window
- Coverage of stdio, Streamable HTTP, WebSocket and HTTP/SSE
Install from npm (`npm install -g mcp-reticle`), PyPI (`pip install mcp-reticle`) or Homebrew; macOS, Linux and Windows are all listed. Nothing else — it sits in front of a server you already have. One caution from the project itself: recordings capture tool inputs, tool outputs and server stderr, so treat the exports as sensitive artefacts rather than ordinary logs.
One command — npm install -g mcp-reticle