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. It enables seamless integration with any MCP client (Claude, Cline, Cursor, etc.) while providing management capabilities through the plugged.in ecosystem. Hub pillars include Knowledge (AI document exchange and RAG v2), Memory (persistent, workspace-scoped memory), and Tools (discovery, templates, prompts) with a proxy layer for a single connection per client. The proxy supports STDIO and Streamable HTTP transports, optional API authentication, multi-workspace configurations, and a unified catalog for tools, resources, templates, and prompts. It leverages API-driven capability discovery via the plugged.in App rather than direct discovery, and provides an interactive playground for testing MCP tools and debugging custom MCP servers. It also offers security features, health monitoring, and a play-ready environment for building and testing MCP servers.