MCP Reticle

Install the Reticle binary using your preferred package manager. The npm package, PyPI package, and Homebrew formula all install the same mcp-reticle CLI.

npm install -g mcp-reticle
# or: pip install mcp-reticle
# or: brew install labterminal/mcp-reticle/mcp-reticle

Instead of pointing your client directly at the MCP server command, wrap it with mcp-reticle run. Reticle acts as a transparent proxy — your client connects to Reticle, which forwards all traffic to the real server and records everything.

mcp-reticle run --name my-server -- npx -y @modelcontextprotocol/server-filesystem /Users/me/work

Replace the MCP server's original command with the mcp-reticle wrapper in your client config file. Your client will now talk to Reticle, which proxies all traffic to the original server.

{
  "mcpServers": {
    "filesystem": {
      "command": "mcp-reticle",
      "args": ["run", "--name", "filesystem", "--", "npx", "-y", "@modelcontextprotocol/server-filesystem", "/Users/me/work"]
    }
  }
}

In a separate terminal, start the Reticle desktop UI. It will open a browser window showing all intercepted JSON-RPC traffic in real time, with request-response correlation and latency timings.

mcp-reticle ui

For Streamable HTTP or SSE MCP servers, use the proxy subcommand instead. Reticle will listen on a local port and forward traffic upstream, recording everything.

mcp-reticle proxy --name api --upstream http://localhost:8080 --listen 3001

If you only need a traffic log without the interactive UI, add the --log flag. This writes all intercepted messages to stdout, suitable for piping to a file or log aggregator.

mcp-reticle run --log -- npx -y @modelcontextprotocol/server-memory