MCP Log Proxy

What emicklei/mcp-log-proxy MCP server does

The emicklei/mcp-log-proxy MCP server wraps another MCP server that uses the STDIO transport. It forwards the traffic between the MCP client and the target process while presenting the message flow in a Web UI. This makes it suitable for inspecting requests, responses, and proxy error information during local development.

The project currently supports STDIO only. It does not describe support for MCP servers exposed through other transport types.

How it works

Run the proxy with a -command argument containing the complete command line needed to start the target MCP server. For example, the documented form is mcp-log-proxy -command melrose-mcp, provided that both executables are available on the process PATH. The client is then configured to launch mcp-log-proxy rather than launching the target server directly.

After startup, the Web interface is available at http://localhost:5656 by default. The HTTP host, port, page title, and proxy error log path can be changed with the -host, -port, -title, and -log flags.

Multiple instances can run at the same time. Each process registers in .mcp-log-proxy-instances.json in the user's home directory, and the Web UI provides a selector for switching between registered proxies. If a requested HTTP port is already occupied, another port is selected for an additional proxy instance.

Setup and configuration

Install the emicklei/mcp-log-proxy MCP server with Homebrew or Go. The repository documents the following options:

• Homebrew: tap emicklei/tap, then install emicklei/tap/mcp-log-proxy.
• Go: run go install github.com/emicklei/mcp-log-proxy@latest.

A client configuration needs the path to the installed proxy binary. Its arguments should include -command followed by the target MCP server command. The README includes configuration examples for Claude and a command-line example for Goose. Those examples also demonstrate assigning separate ports, titles, and log files to different proxied servers.

Tools and capabilities

The provided MCP tool list contains browser interaction and inspection operations:

• Navigate to URLs and move backward or forward through browser history.
• Capture an accessibility snapshot, click or hover on page elements, type into editable controls, and select dropdown options.
• Press keyboard keys and wait for a specified number of seconds.
• Retrieve browser console logs and capture screenshots.

The project documentation specifically describes the Web UI as a message-flow viewer for proxied MCP traffic. The browser operations listed above are the MCP tools exposed by the supplied listing.

Limitations and notes

The proxy only supports the STDIO interface. The target command must be supplied through -command; examples assume the target executable or command is available at the path used in the configuration. The default Web endpoint binds to localhost on port 5656, although both values can be overridden. Proxy errors can be written to a file with -log, independently of any log arguments passed to the target MCP server.

The emicklei/mcp-log-proxy MCP server is released under the MIT License.