pluggedin-mcp-proxy

plugged.in MCP Proxy Server

📋 Overview

The plugged.in MCP Proxy Server is a powerful middleware that aggregates multiple Model Context Protocol (MCP) servers into a single unified interface. It fetches tool, prompt, and resource configurations from the plugged.in App and intelligently routes requests to the appropriate underlying MCP servers.

This proxy enables seamless integration with any MCP client (Claude, Cline, Cursor, etc.) while providing advanced management capabilities through the plugged.in ecosystem.

✨ Key Features

• Universal MCP Compatibility: Works with any MCP client including Claude Desktop, Cline, and Cursor
• Multi-Server Support: Connect both STDIO (command-line) and WebSocket (HTTP-based) MCP servers
• Namespace Isolation: Keep joined MCPs separate and organized with proper prefixing
• Multi-Workspace Layer: Switch between different sets of MCP configurations with one click
• Simplified Architecture: Streamlined codebase with improved startup time and reduced complexity
• API-Driven Proxy: Fetches capabilities from plugged.in App APIs rather than direct discovery
• Full MCP Support: Handles tools, resources, resource templates, and prompts
• Custom Instructions: Supports server-specific instructions formatted as MCP prompts

🚀 Quick Start

Prerequisites

• Node.js 18+ (recommended v20+)
• An API key from the plugged.in App (get one at plugged.in/api-keys)

Installation

Configuration for MCP Clients

Claude Desktop

Add the following to your Claude Desktop configuration:

Cline

Add the following to your Cline configuration:

Cursor

For Cursor, you can use command-line arguments instead of environment variables:

⚙️ Configuration Options

Environment Variables

Command Line Arguments

Command line arguments take precedence over environment variables:

For a complete list of options:

🐳 Docker Usage

You can also build and run the proxy server using Docker.

Building the Image

Ensure you have Docker installed and running. Navigate to the pluggedin-mcp directory and run:

A .dockerignore file is included to optimize the build context.

Running the Container

Run the container, providing the necessary environment variables:

Replace YOUR_API_KEY and YOUR_API_BASE_URL (if not using the default https://plugged.in).

Testing with MCP Inspector

While the container is running, you can connect to it using the MCP Inspector:

This will connect to the standard input/output of the running container.

Stopping the Container

Press Ctrl+C in the terminal where docker run is executing. The --rm flag ensures the container is removed automatically upon stopping.

🏗️ System Architecture

The plugged.in MCP Proxy Server acts as a bridge between MCP clients and multiple underlying MCP servers:

🔄 Workflow

1. Configuration: The proxy fetches server configurations from the plugged.in App
2. Capability Listing: The proxy fetches discovered capabilities from plugged.in App APIs
   • tools/list: Fetches from /api/tools (returns prefixed names)
   • resources/list: Fetches from /api/resources
   • resource-templates/list: Fetches from /api/resource-templates
   • prompts/list: Fetches from /api/prompts and /api/custom-instructions, merges results
3. Capability Resolution: The proxy resolves capabilities to target servers
   • tools/call: Parses prefix from tool name, looks up server in internal map
   • resources/read: Calls /api/resolve/resource?uri=... to get server details
   • prompts/get: Checks for custom instruction prefix or calls /api/resolve/prompt?name=...
4. Request Routing: Requests are routed to the appropriate underlying MCP server
5. Response Handling: Responses from the underlying servers are returned to the client

🧩 Integration with plugged.in App

The plugged.in MCP Proxy Server is designed to work seamlessly with the plugged.in App, which provides:

• A web-based interface for managing MCP server configurations
• Centralized capability discovery (Tools, Resources, Templates, Prompts)
• Custom instructions management
• Multi-workspace support for different configuration sets
• An interactive playground for testing MCP tools
• User authentication and API key management

📚 Related Resources

• plugged.in App Repository
• Model Context Protocol (MCP) Specification
• Claude Desktop Documentation
• Cline Documentation

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgements

• Inspired by the MCP Proxy Server
• Built on the Model Context Protocol