Mcp Log Proxy

What is Mcp Log Proxy?

Mcp Log Proxy is a debugging tool that intercepts and visualizes all messages exchanged between a MCP client and a MCP server through a Web interface. It currently supports only the STDIO transport. It is intended for developers who need to inspect or troubleshoot MCP protocol traffic.

How to use Mcp Log Proxy?

Install via Homebrew (brew tap "emicklei/tap" then brew install emicklei/tap/mcp-log-proxy) or with Go (go install github.com/emicklei/mcp-log-proxy@latest). Run the proxy with the required -command flag, providing the full command line to start the target MCP server (e.g., mcp-log-proxy -command melrose-mcp). Messages are then viewable at http://localhost:5656. Optional flags include -host, -port, -title, and -log.

Key features of Mcp Log Proxy

• Visualizes MCP client–server messages in a web UI.
• Auto-detects and avoids port conflicts when multiple proxies run.
• Registers all running proxy instances in a home‑directory JSON file.
• Supports overriding HTTP host, port, web page title, and proxy log file.
• Compatible with any STDIO‑based MCP server.

Use cases of Mcp Log Proxy

• Debugging MCP protocol traffic during development.
• Monitoring messages between a client (e.g., Claude) and a custom MCP server.
• Troubleshooting integration issues with multiple MCP servers simultaneously.
• Inspecting error information that appears in the log proxy’s web view.

FAQ from Mcp Log Proxy

What transport does Mcp Log Proxy support?

It currently only supports the STDIO interface for proxying MCP messages.

How do I install Mcp Log Proxy?

Install via Homebrew (brew tap "emicklei/tap" then brew install emicklei/tap/mcp-log-proxy) or with Go (go install github.com/emicklei/mcp-log-proxy@latest).

How do I view the proxied messages?

After starting the proxy, open a browser to http://localhost:5656 (or the configured host and port) to see the web log view.

Can I run multiple Mcp Log Proxy instances at the same time?

Yes. Each instance registers itself in .mcp-log-proxy-instances.json in your home directory. The web page includes a selector to switch between running proxies, and the proxy automatically chooses an available port if the default is taken.

Where does Mcp Log Proxy store its instance registration?

In the file .mcp-log-proxy-instances.json located in your home directory.