MCP Client Router

The MCP Client Router is a transport interface for aggregating multiple Model Context Protocol (MCP) clients into a single unified interface. It allows you to seamlessly interact with multiple MCP servers through a single client interface.

Features

• Route calls to the appropriate MCP client based on prefixed names
• Aggregate tools, prompts, and resources from multiple clients
• Prefix/suffix naming convention to route requests to the correct client
• Implementation of the MCP Transport interface for seamless integration
• Support for both HTTP and stdio-based MCP servers

Installation

npm install mcp-client-router

Usage

Basic Usage

import { ClientRouter } from "mcp-client-router";
import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

// Create individual clients
const client1 = new Client({ name: "client1", version: "1.0.0" });
const client2 = new Client({ name: "client2", version: "1.0.0" });

// Connect them to their respective transports
await client1.connect(
  new StdioClientTransport({
    command: "node",
    args: ["server1.js"],
  })
);

await client2.connect(
  new StdioClientTransport({
    command: "node",
    args: ["server2.js"],
  })
);

// Create a router with the clients
const router = new ClientRouter([client1, client2]);

// Now you can use the router as a unified client
const allTools = await router.listTools();
// Tools will be prefixed with client names, e.g., "client1__toolName"

// To call a specific tool
const result = await router.callTool({
  name: "client1__toolName",
  arguments: {
    /* args */
  },
});

Creating from Configuration Object

import { fromObject } from "mcp-client-router";

const router = await fromObject({
  mcpServers: {
    client1: {
      command: "node",
      args: ["server1.js"],
    },
    client2: {
      url: "http://localhost:3000/mcp",
    },
  },
});

// Now use the router as a unified client

Connecting to a Server Transport

import { ClientRouter } from "mcp-client-router";
import { HTTPServerTransport } from "@modelcontextprotocol/sdk/server/http.js";

// Create router with clients
const router = new ClientRouter([
  /* clients */
]);

// Connect to an HTTP server transport
const httpTransport = await router.connect(HTTPServerTransport, {
  port: 3000,
  path: "/mcp",
});

// The router now acts as an MCP server

How It Works

The Client Router prefixes the names of tools, prompts, and resources with the client name followed by a double underscore (__). For example:

• A tool named analyze from client client1 becomes client1__analyze
• A prompt named greeting from client client2 becomes client2__greeting
• A resource with URI docs/api.md from client client3 becomes client3__docs/api.md

When you call a prefixed tool/prompt/resource, the Client Router routes the call to the appropriate client.

API Reference

ClientRouter

The main class that implements the MCP Transport interface.

new ClientRouter((clients = []));

Methods

• start(): Starts processing messages on the transport
• send(message, options): Sends a JSON-RPC message
• close(): Closes all client connections
• connect(transportOrConstructor, options): Connects to a server transport

fromObject(obj, options)

Creates a ClientRouter from a configuration object.

License

ISC