MCP Client Connector

A flexible client connector for Model Context Protocol (MCP) servers with support for multiple transport methods.

Features

• Connect to MCP servers via SSE, WebSocket, or stdio
• Support for both remote servers and local processes
• Automatic package version resolution
• Custom logging support
• Error handling with detailed stderr logs

Installation

npm install @yepcode/mcp-client-connector

Usage

Connect to a remote MCP server

import { MCPClientConnector } from 'mcp-client-connector';

// Connect to a remote MCP server via HTTP/SSE
const connector = new MCPClientConnector({
  remoteUrl: 'https://your-mcp-server.com/endpoint'
});

// Connect to a remote MCP server via WebSocket
const wsConnector = new MCPClientConnector({
  remoteUrl: 'wss://your-mcp-server.com/socket'
});

try {
  const client = await connector.connect();

  // Use the MCP client
  const result = await client.invoke('some_tool', {
    param1: 'value1',
    param2: 'value2'
  });

  console.log(result);

  // Close the connection when done
  await connector.close();
} catch (error) {
  console.error('Error connecting to MCP server:', error);
}

Run a local MCP server process

import { MCPClientConnector } from 'mcp-client-connector';

// Connect to a local JavaScript MCP server
const connector = new MCPClientConnector({
  language: 'javascript',
  package: 'your-mcp-server-package',
  version: '1.0.0', // optional, will use latest if not specified
  commandArgs: '--some-flag', // optional
  envVars: { API_KEY: 'your-api-key' } // optional
});

try {
  const client = await connector.connect();

  // Use the MCP client
  const result = await client.invoke('some_tool', {
    param1: 'value1',
    param2: 'value2'
  });

  console.log(result);

  // Close the connection when done
  await connector.close();
} catch (error) {
  console.error('Error connecting to MCP server:', error);

  // Access stderr logs if available
  if (error instanceof MCPError) {
    console.error('Stderr logs:', error.stderrLogs);
  }
}

Custom Logging

import { MCPClientConnector, Logger } from 'mcp-client-connector';

// Implement your own logger
class MyCustomLogger implements Logger {
  info(message: string, ...args: any[]): void {
    // Custom info logging implementation
    myLoggingService.log('INFO', message, ...args);
  }

  error(message: string, ...args: any[]): void {
    // Custom error logging implementation
    myLoggingService.log('ERROR', message, ...args);
  }
}

// Use your custom logger
const connector = new MCPClientConnector({
  remoteUrl: 'https://your-mcp-server.com/endpoint',
  logger: new MyCustomLogger()
});

// The rest of your code...

API Reference

MCPClientConnector

The main class for connecting to MCP servers.

Constructor

constructor(options: MCPClientConnectorOptions)

Options

• RemoteMCPClientConnectorOptions

  • remoteUrl: string - The URL of the remote MCP server
  • logger?: Logger - Optional custom logger implementation

• StdioMCPClientConnectorOptions

  • language: string - The language of the MCP server package ('javascript' or 'python')
  • package: string - The name of the MCP server package
  • version?: string - Optional specific version of the package
  • commandArgs?: string - Optional command line arguments
  • envVars?: EnvVars | string - Optional environment variables
  • logger?: Logger - Optional custom logger implementation

Methods

• connect(): Promise<Client> - Connect to the MCP server
• close(): Promise<void> - Close the connection
• getStderrLogs(): string[] - Get any stderr logs from the MCP server (stdio only)

Logger Interface

interface Logger {
  info(message: string, ...args: any[]): void;
  error(message: string, ...args: any[]): void;
}

License

MIT