MCP Proxy Server

What is MCP Proxy Server?

An MCP proxy server that aggregates and serves multiple MCP resource servers through a single unified interface. It acts as a central hub for connecting, managing, and routing requests to backend MCP servers, handling resource management, tool aggregation, and prompt handling.

How to use MCP Proxy Server?

Configure the proxy by copying config.example.json to config.json and listing the backend MCP servers with their transport details (command, args, env for stdio; url for SSE). Run the server with MCP_CONFIG_PATH=./config.json mcp-proxy-server. For Claude Desktop, add an entry for mcp-proxy in claude_desktop_config.json with the absolute path to the proxy build and config file.

Key features of MCP Proxy Server

• Discover and connect to multiple MCP resource servers.
• Aggregate resources from all connected servers.
• Expose tools from all servers with automatic routing.
• Aggregate prompts from all connected servers.
• Support both stdio and SSE backend transports.
• Maintain consistent URI schemes across servers.

Use cases of MCP Proxy Server

• Centralize multiple MCP servers behind a single endpoint.
• Route tool calls and prompts to the correct backend server.
• Aggregate resources from different data sources into one interface.
• Simplify client configuration by managing many servers through one proxy.

FAQ from MCP Proxy Server

How do I configure the proxy server?

Create a JSON config file listing each backend server with its name and transport (command+args or SSE url). Provide the path via the MCP_CONFIG_PATH environment variable when running mcp-proxy-server.

What transport types does the proxy support?

Backend servers can use stdio (command with optional args and env) or SSE (URL). The proxy itself communicates with clients via stdio by default, with optional SSE for development (npm run dev:sse).

How can I debug the proxy server?

Use the MCP Inspector by running npm run inspector. It provides a URL for debugging tools, which is recommended since MCP servers communicate over stdio.

What does the KEEP_SERVER_OPEN environment variable do?

Setting KEEP_SERVER_OPEN=1 keeps the SSE server running even if a client disconnects, useful when multiple clients connect to the proxy.

How do I set up the proxy for Claude Desktop?

Add an entry under mcpServers in the Claude Desktop config file (MacOS: ~/Library/Application Support/Claude/claude_desktop_config.json, Windows: %APPDATA%/Claude/claude_desktop_config.json) with the command pointing to the proxy build and the absolute config path.