What it does

mcp-proxy is a transport bridge for the Model Context Protocol that translates between stdio and SSE (Server-Sent Events) or Streamable HTTP protocols. It operates in two modes: stdio-to-SSE allows MCP clients like Claude Desktop to communicate with remote SSE-based MCP servers without native support; SSE-to-stdio converts a local stdio MCP server into an SSE endpoint, enabling remote clients and LLM services to reach it over HTTP.

Who it's for

Claude Desktop users and MCP client developers integrating with remote SSE-based servers; infrastructure teams exposing local stdio MCP servers to remote clients over the network.

Common use cases

Connect Claude Desktop to a remote SSE MCP server without native protocol support
Expose a local stdio MCP server as an HTTP endpoint for remote LLM clients
Bridge MCP servers and clients using incompatible transport protocols
Route MCP traffic through firewalls or network boundaries that enforce HTTP

Setup pitfalls

Must specify the correct SSE endpoint URL and transport type; use --transport=streamablehttp if the server requires it
Authentication requires explicit configuration via --headers or the API_ACCESS_TOKEN environment variable for bearer tokens
Port conflicts in SSE-to-stdio mode—confirm the --sse-port is available before starting
In SSE-to-stdio mode, pass environment variables for the local server via --env flags before the -- separator