MCP Local Router

What is MCP Local Router?

MCP Local Router is an aggregation proxy for MCP (Model Context Protocol) servers. It connects to multiple upstream MCP servers and combines their functionalities into a single interface for downstream clients.

How to use MCP Local Router?

Run the router with a JSON configuration file and specify the transport: cargo run -- --config mcp-config.json --transport stdio or --transport sse. The configuration file defines each upstream server with command, args, and env fields. For SSE transport, the router exposes aggregated (/sse) and per‑upstream (/sse/{serverName}) endpoints.

Key features of MCP Local Router

• Supports configuration file specified via command‑line argument.
• Configures multiple upstream MCP servers from one JSON file.
• Supports stdio transport with optional environment variable injection.
• Supports SSE transport with aggregated /sse and per‑upstream /sse/{serverName} endpoints.
• All SSE connections share a single POST /message?sessionId=… channel.

Use cases of MCP Local Router

• Aggregate several MCP servers (e.g., filesystem, database) into a single service.
• Route a client to a specific upstream server using the per‑upstream SSE path.
• Test or develop multiple MCP servers together without separate client wiring.
• Inject different environment variables per upstream server for credential isolation.

FAQ from MCP Local Router

What does MCP Local Router do?

It acts as a local proxy that aggregates multiple upstream MCP servers, presenting their combined tools and resources to a client through a single transport endpoint.

What transports are supported?

It supports stdio transport and SSE (Server‑Sent Events) transport. The SSE mode provides both an aggregated stream and individual per‑server streams.

What are the runtime dependencies?

The project is built with Rust 2021 Edition, uses the tokio async runtime, and the rmcp library for MCP protocol handling.

How is the configuration file structured?

The configuration file is JSON with a top‑level "mcpServers" object. Each key is the server name, and the value contains command (the executable), args (command arguments array), and env (environment variable map).

How do I build the router?

Clone the repository and run cargo build --release. The binary will be placed in target/release/.