What is Mcp Proxy Sidecar

mcp-proxy-sidecar is a fork of the JetBrains MCP Server that enhances it with real-time WebSocket monitoring capabilities for all MCP interactions.

Use cases

Use cases include debugging MCP interactions, monitoring performance of tool calls, and enhancing development workflows by providing insights into the communication between MCP Clients and JetBrains IDE.

How to use

To use mcp-proxy-sidecar, integrate it with your MCP Client (like Claude Desktop App) and configure it to communicate with the JetBrains IDE. WebSocket notifications will be available on port 27042 for monitoring tool calls.

Key features

Key features include real-time WebSocket notifications for all MCP tool calls, detailed information about endpoints and arguments, and full compatibility with the original MCP Server functionality.

Where to use

mcp-proxy-sidecar is suitable for development environments where real-time monitoring of MCP interactions is required, particularly in applications using JetBrains IDEs.

MCP Proxy Sidecar

A fork of the JetBrains MCP Server that adds WebSocket monitoring capabilities, created by @dortegau.

This project extends the original MCP server functionality with WebSocket support while maintaining compatibility with all features of the original implementation.

Architecture

graph LR
    A[MCP Client<br>e.g. Claude<br>Desktop App]
    B[MCP Proxy<br>Sidecar<br>with WebSocket]
    C[JetBrains IDE]
    D[WebSocket Clients<br>Monitoring]
    
    A <--MCP requests/responses--> B
    B <--IDE commands/responses--> C
    B --WebSocket notifications<br>port 27042--> D

    style A fill:#f5f5f5,stroke:#333,stroke-width:2px
    style B fill:#e1f5fe,stroke:#333,stroke-width:2px
    style C fill:#f5f5f5,stroke:#333,stroke-width:2px
    style D fill:#f5f5f5,stroke:#333,stroke-width:2px

The diagram above illustrates the system architecture and data flow:

1. MCP Clients (like Claude Desktop App) communicate with the Sidecar using MCP protocol
2. The Sidecar translates and forwards commands to JetBrains IDE
3. Responses from the IDE are sent back through the Sidecar
4. All tool calls are broadcasted via WebSocket for monitoring purposes

Features

This fork adds WebSocket notifications that allow you to monitor all MCP tool calls in real-time. Each tool call is broadcasted through WebSocket with detailed information about the endpoint and arguments.

WebSocket Message Format

interface MCPNotification {
  type: 'mcp-notification';
  payload: {
    endpoint: string;     // Tool name that was called
    content: any;         // Call arguments
    timestamp: string;    // ISO timestamp
  }
}

WebSocket Configuration

The WebSocket server runs on port 27042 by default. You can customize this port using the WS_PORT environment variable in your configuration:

Usage

Install MCP Server Plugin

https://plugins.jetbrains.com/plugin/26071-mcp-server

Usage with Claude Desktop

To use this with Claude Desktop, add the following to your claude_desktop_config.json.
The full path on MacOS: ~/Library/Application\ Support/Claude/claude_desktop_config.json, on Windows: %APPDATA%/Claude/claude_desktop_config.json.

Configuration Options

The following environment variables can be configured in your claude_desktop_config.json:

Example configuration with all options:

{
  "mcpServers": {
    "ide": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-proxy-sidecar"
      ],
      "env": {
        "WS_PORT": "27042",
        "IDE_PORT": "63342",
        "HOST": "127.0.0.1",
        "LOG_ENABLED": "true"
      }
    }
  }
}

Note: If IDE_PORT is not specified, the sidecar will automatically scan ports 63342-63352 to find the IDE.

Development

Requirements

• Node.js 20.x
• pnpm (latest version)

Build

1. Install dependencies:

   pnpm install --frozen-lockfile
   

2. Build the project:

   pnpm build
   

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Publishing

This package is published to npm with:

• Provenance enabled for supply chain security
• Automated releases via GitHub Actions when creating a new release
• Public access on npm registry

To publish a new version:

1. Update version in package.json
2. Create and push a new tag matching the version
3. Create a GitHub release from the tag
4. The workflow will automatically build and publish to npm

Changelog

1.0.0

• Initial fork from @jetbrains/mcp-proxy
• Added WebSocket support for real-time tool call monitoring
• Renamed package for clarity
• Updated documentation and configuration examples

Credits

This is a fork of the JetBrains MCP Proxy Server. All credit for the original implementation goes to the JetBrains team.