Plugged.in

Acts as a centralized proxy that aggregates multiple downstream MCP servers into a single MCP interface, routing client requests to appropriate servers based on tool/resource ownership. Uses a request routing decision tree that determines whether to handle requests internally (built-in tools) or forward to downstream servers, with automatic server discovery via the plugged.in Registry v2 API and bidirectional notification synchronization across all connected servers.

Supports both STDIO and HTTP transport modes simultaneously, allowing the same proxy instance to serve desktop clients (Claude, Cline) via process-based stdio streams and remote/web clients via HTTP on port 12006. Uses session-based HTTP management for stateful connections and process-based streaming for stdio, with automatic transport negotiation based on client connection type.

Monitors the health and availability of connected downstream MCP servers, detecting disconnections and server failures. Implements automatic reconnection logic with exponential backoff, maintains server status metadata (online/offline), and excludes unavailable servers from tool discovery and request routing. Provides health check endpoints for monitoring proxy and downstream server status without requiring manual intervention.

Discovers and aggregates resources and prompts from all connected downstream MCP servers, exposing them through unified GetResource and GetPrompt handlers. Maintains a registry of available resources and prompts with server attribution, similar to tool discovery. Routes resource and prompt requests to the correct server based on ownership metadata, with proper error handling for resources/prompts not found.

Discovers and catalogs all tools, resources, and prompts from connected downstream MCP servers, exposing them through a unified discovery interface. Implements a tool registry that tracks tool ownership, metadata, and availability across servers, with real-time synchronization when servers connect/disconnect. Distinguishes between built-in proxy tools (discovery, management) and downstream server tools, preventing namespace collisions through server-prefixed tool naming when needed.

Integrates deeply with the plugged.in App ecosystem through Registry v2 API, providing automatic OAuth token management, real-time activity/usage tracking, and bidirectional notifications. Automatically retrieves and refreshes OAuth tokens via /api/oauth/tokens, tracks tool usage via /api/activity endpoint, and synchronizes notifications across the proxy and plugged.in platform. Enables server discovery through plugged.in Registry without manual configuration.

Provides a set of built-in tools that operate on the proxy itself (distinct from downstream server tools), including server discovery, tool listing, configuration management, and debugging utilities. These tools are handled internally by the proxy without forwarding to downstream servers, enabling meta-operations like listing all connected servers, checking server health, and managing proxy configuration through the MCP interface itself.

Implements a sophisticated request routing decision tree that determines whether to handle MCP requests internally (built-in tools) or forward them to appropriate downstream servers based on tool/resource/prompt ownership. Routes CallTool, GetResource, and GetPrompt requests to the correct server, with fallback handling for tools not found and automatic error propagation. Maintains request context and metadata throughout the routing process for logging and debugging.

Logs all MCP activity (tool calls, resource access, prompt usage) with timestamps and server attribution, sending real-time notifications to the plugged.in platform via /api/notifications endpoint. Implements bidirectional notification synchronization, allowing the proxy to receive notifications from plugged.in and forward them to connected clients. Maintains activity history for audit trails and analytics without persistent storage (requires external state store for long-term retention).

Provides an interactive debugging interface (MCP Inspector) for testing MCP requests, inspecting server responses, and validating tool schemas without deploying to production. Allows developers to simulate tool calls, view request/response payloads, and debug routing issues in real-time. Integrated into the proxy for immediate feedback during MCP server development and integration testing.

Supports multiple deployment modes (NPM, Docker, Smithery) with environment variable-based configuration, allowing the same codebase to be deployed across different environments without code changes. Reads configuration from environment variables for server endpoints, API credentials, transport modes, and ecosystem integration settings. Enables rapid deployment through Docker containers or Smithery package manager with minimal configuration overhead.

Manages multiple concurrent MCP client connections (Claude Desktop, Cline, Cursor) with session-based state management for HTTP transport and process-based streaming for stdio. Handles client connection lifecycle (connect, disconnect, timeout), maintains per-client context for request routing, and implements session persistence for HTTP clients. Supports multiple simultaneous clients without cross-contamination of request context or session state.