MCP Hub

A centralized manager for Model Context Protocol (MCP) servers that provides:

• Dynamic MCP server management and monitoring
• REST API for tool execution and resource access
• MCP Server marketplace (using Cline marketplace)
• Real-time server status tracking
• Client connection management
• Process lifecycle handling

Overview

Hub Server vs MCP Servers

• Hub Server (MCP Hub)

  • Central management server that connects to and manages multiple MCP servers
  • Provides unified API endpoints for clients to access MCP server capabilities
  • Handles server lifecycle, health monitoring, and client connections
  • Routes requests between clients and appropriate MCP servers

• MCP Servers

  • Individual servers that provide specific tools and resources
  • Each server has its own capabilities (tools, resources, templates)
  • Connected to and managed by the Hub server
  • Process requests from clients through the Hub

Installation

npm install -g mcp-hub

Basic Usage

Start the hub server:

mcp-hub --port 3000 --config path/to/config.json

CLI Options

Options:
  --port            Port to run the server on (default: 3000)
  --config          Path to config file (required)
  --watch           Watch config file for changes (default: false)
  --shutdown-delay  Delay in milliseconds before shutting down when no clients are connected (default: 0)
  -h, --help       Show help information

The server outputs JSON-formatted status messages on startup and state changes:

{
  "status": "ready",
  "server_id": "mcp-hub",
  "version": "1.0.0",
  "port": 3000,
  "pid": 12345,
  "servers": [],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Nix

Nixpkgs install

coming...

Flake install

Just add it to your NixOS flake.nix or home-manager:

inputs = {
  mcp-hub.url = "github:ravitemer/mcp-hub";
  ...
}

To integrate mcp-hub to your NixOS/Home Manager configuration, add the following to your environment.systemPackages or home.packages respectively:

inputs.mcp-hub.packages."${system}".default

Usage without install

If you want to use mcphub.nvim without having mcp-hub server in your PATH you can link the server under the hood adding the mcp-hub nix store path to the cmd command in the plugin config like

Nixvim example:

{ mcphub-nvim, mcp-hub, ... }:
{
  extraPlugins = [mcphub-nvim];
  extraConfigLua = ''
    require("mcphub").setup({
        port = 3000,
        config = vim.fn.expand("~/mcp-hub/mcp-servers.json"),
        cmd = "${mcp-hub}/bin/mcp-hub"
    })
  '';
}

# where
{
  # For nixpkgs (not available yet)
  mcp-hub = pkgs.mcp-hub;

  # For flakes
  mcp-hub = inputs.mcp-hub.packages."${system}".default;
}

Configuration

MCP Hub uses a JSON configuration file to define managed servers:

{
  "mcpServers": {
    "stdio-server": {
      "command": "npx",
      "args": ["example-server"],
      "env": {
        "API_KEY": "", // Will use process.env.API_KEY
        "DEBUG": "true", // Will use this value
        "SECRET_TOKEN": null // Will use process.env.SECRET_TOKEN
      },
      "disabled": false
    },
    "sse-server": {
      "url": "https://api.example.com/mcp",
      "headers": {
        "Authorization": "Bearer token",
        "Content-Type": "application/json"
      },
      "disabled": false
    }
  }
}

Configuration Options

MCP Hub supports two types of servers: STDIO (local) and SSE (remote). The server type is automatically determined based on the configuration fields provided.

STDIO Server Options

• command: Command to start the local MCP server
• args: Array of command line arguments
• env: Environment variables for the server. If a variable is specified with a falsy value (empty string, null, undefined), it will fall back to using the corresponding system environment variable if available.
• disabled: Whether the server is disabled (default: false)

SSE Server Options

• url: The URL of the remote SSE server endpoint
• headers: Optional HTTP headers for the SSE connection (e.g., for authentication)
• disabled: Whether the server is disabled (default: false)

Server Type Detection

The server type (STDIO or SSE) is automatically determined based on the presence of specific fields:

• If command is present → STDIO server
• If url is present → SSE server

Note: A server configuration cannot mix STDIO and SSE fields - it must be one type or the other.

Example Integrations

Neovim Integration

The ravitemer/mcphub.nvim plugin provides seamless integration with Neovim, allowing direct interaction with MCP Hub from your editor:

• Execute MCP tools directly from Neovim
• Access MCP resources within your editing workflow
• Real-time status updates in Neovim
• Auto install mcp servers with marketplace addition

Logging

MCP Hub uses structured JSON logging for all events:

{
  "type": "error",
  "code": "TOOL_ERROR",
  "message": "Failed to execute tool",
  "data": {
    "server": "example-server",
    "tool": "example-tool",
    "error": "Invalid parameters"
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Log levels include:

• info: Normal operational messages
• warn: Warning conditions
• debug: Detailed debug information
• error: Error conditions (includes error code and details)

REST API

Health and Status

Health Check

GET /api/health

Response:

{
  "status": "ok",
  "server_id": "mcp-hub",
  "version": "1.0.0",
  "activeClients": 2,
  "timestamp": "2024-02-20T05:55:00.000Z",
  "servers": []
}

List MCP Servers

GET /api/servers

Get Server Info

POST /api/servers/info
Content-Type: application/json

{
  "server_name": "example-server"
}

Refresh Server Capabilities

POST /api/servers/refresh
Content-Type: application/json

{
  "server_name": "example-server"
}

Response:

{
  "status": "ok",
  "server": {
    "name": "example-server",
    "capabilities": {
      "tools": ["tool1", "tool2"],
      "resources": ["resource1", "resource2"],
      "resourceTemplates": []
    }
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Refresh All Servers

POST /api/refresh

Response:

{
  "status": "ok",
  "servers": [
    {
      "name": "example-server",
      "capabilities": {
        "tools": ["tool1", "tool2"],
        "resources": ["resource1", "resource2"],
        "resourceTemplates": []
      }
    }
  ],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Start Server

POST /api/servers/start
Content-Type: application/json

{
  "server_name": "example-server"
}

Response:

{
  "status": "ok",
  "server": {
    "name": "example-server",
    "status": "connected",
    "uptime": 123
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Stop Server

POST /api/servers/stop?disable=true|false
Content-Type: application/json

{
  "server_name": "example-server"
}

The optional disable query parameter can be set to true to disable the server in the configuration.

Response:

{
  "status": "ok",
  "server": {
    "name": "example-server",
    "status": "disconnected",
    "uptime": 0
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Client Management

Register Client

POST /api/client/register
{
  "clientId": "unique_client_id"
}

Unregister Client

POST /api/client/unregister
{
  "clientId": "unique_client_id"
}

Marketplace Integration

List Available Servers

GET /api/marketplace

Query Parameters:

• search: Filter by name, description, or tags
• category: Filter by category
• tags: Filter by comma-separated tags
• sort: Sort by "newest", "stars", or "name"

Response:

{
  "items": [
    {
      "mcpId": "github.com/user/repo/server",
      "name": "Example Server",
      "description": "Description here",
      "category": "search",
      "tags": ["search", "ai"],
      "githubStars": 100,
      "isRecommended": true,
      "createdAt": "2024-02-20T05:55:00.000Z"
    }
  ],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Get Server Details

POST /api/marketplace/details
Content-Type: application/json

{
  "mcpId": "github.com/user/repo/server"
}

Response:

{
  "server": {
    "mcpId": "github.com/user/repo/server",
    "name": "Example Server",
    "description": "Description here",
    "githubUrl": "https://github.com/user/repo",
    "readmeContent": "# Server Documentation...",
    "llmsInstallationContent": "Installation guide..."
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

MCP Server Operations

Execute Tool

POST /api/servers/tools
Content-Type: application/json

{
  "server_name": "example-server",
  "tool": "tool_name",
  "arguments": {}
}

Access Resource

POST /api/servers/resources
Content-Type: application/json

{
  "server_name": "example-server",
  "uri": "resource://uri"
}

Get Prompt

POST /api/servers/prompts
Content-Type: application/json

{
  "server_name": "example-server",
  "prompt": "prompt_name",
  "arguments": {}
}

Response:

{
  "result": {
    "messages": [
      {
        "role": "assistant",
        "content": {
          "type": "text",
          "text": "Text response example"
        }
      },
      {
        "role": "assistant",
        "content": {
          "type": "image",
          "data": "base64_encoded_image_data",
          "mimeType": "image/png"
        }
      }
    ]
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Restart Hub

POST /api/restart

Reloads the configuration file and restarts all MCP servers.

Response:

{
  "status": "ok",
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Real-time Updates

The Hub Server provides real-time updates via Server-Sent Events (SSE) at /api/events. Connect to this endpoint to receive real-time updates about server status, client connections, and capability changes.

Event Types

1. server_info - Initial connection information

{
  "server_id": "mcp-hub",
  "version": "1.0.0",
  "status": "connected",
  "pid": 12345,
  "port": 3000,
  "activeClients": 1,
  "timestamp": "2024-02-20T05:55:00.000Z"
}

2. server_ready - Server started and ready

{
  "status": "ready",
  "server_id": "mcp-hub",
  "version": "1.0.0",
  "port": 3000,
  "pid": 12345,
  "servers": [],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

3. client_registered/unregistered - Client connection events

{
  "activeClients": 2,
  "clientId": "client_123",
  "timestamp": "2024-02-20T05:55:00.000Z"
}

4. tool_list_changed - Server's tools list has changed

{
  "type": "TOOL",
  "server": "example-server",
  "tools": ["tool1", "tool2"],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

5. resource_list_changed - Server's resources list has changed

{
  "type": "RESOURCE",
  "server": "example-server",
  "resources": ["resource1", "resource2"],
  "resourceTemplates": [],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

6. prompt_list_changed - Server's prompts list has changed

{
  "type": "PROMPT",
  "server": "example-server",
  "prompts": ["prompt1", "prompt2"],
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Error Handling

MCP Hub implements a comprehensive error handling system with custom error classes for different types of errors:

Error Classes

• ConfigError: Configuration-related errors (invalid config, missing fields)
• ConnectionError: Server connection issues (failed connections, transport errors)
• ServerError: Server startup/initialization problems
• ToolError: Tool execution failures
• ResourceError: Resource access issues
• ValidationError: Request validation errors

Each error includes:

• Error code for easy identification
• Detailed error message
• Additional context in the details object
• Stack trace for debugging

Example error structure:

{
  "code": "CONNECTION_ERROR",
  "message": "Failed to communicate with server",
  "details": {
    "server": "example-server",
    "error": "connection timeout"
  },
  "timestamp": "2024-02-20T05:55:00.000Z"
}

Error Categories

1. Configuration Errors

   • Invalid config format
   • Missing required fields
   • Environment variable issues

2. Server Management Errors

   • Connection failures
   • Lost connections
   • Capability fetch issues
   • Server startup problems

3. Request Processing Errors

   • Invalid parameters
   • Server availability
   • Tool execution failures
   • Resource access issues

4. Client Management Errors

   • Registration failures
   • Duplicate registrations
   • Invalid client IDs

Architecture

Hub Server Lifecycle

sequenceDiagram
    participant H as Hub Server
    participant M1 as MCP Server 1
    participant M2 as MCP Server 2
    participant C as Client

    Note over H: Server Start
    activate H
    H->>+M1: Connect
    M1-->>-H: Connected + Capabilities
    H->>+M2: Connect
    M2-->>-H: Connected + Capabilities

    Note over C,H: Client Interactions
    C->>H: Register Client
    H-->>C: Servers List & Capabilities
    
    C->>H: Call Tool (M1)
    H->>M1: Execute Tool
    M1-->>H: Tool Result
    H-->>C: Response

    C->>H: Access Resource (M2)
    H->>M2: Get Resource
    M2-->>H: Resource Data
    H-->>C: Response

    Note over H: Server Management
    H->>H: Monitor Server Health
    H->>H: Track Server Status
    H->>H: Update Capabilities

    Note over H: Shutdown Process
    C->>H: Unregister
    H->>M1: Disconnect
    H->>M2: Disconnect
    deactivate H

The Hub Server coordinates communication between clients and MCP servers:

1. Starts and connects to configured MCP servers
2. Manages client registrations
3. Routes tool execution and resource requests
4. Handles server monitoring and health checks
5. Performs clean shutdown of all connections

MCP Server Management

flowchart TB
    A[Hub Server Start] --> B{Config Available?}
    B -->|Yes| C[Load Server Configs]
    B -->|No| D[Use Default Settings]
    
    C --> E[Initialize Connections]
    D --> E
    
    E --> F{For Each MCP Server}
    F -->|Enabled| G[Attempt Connection]
    F -->|Disabled| H[Skip Server]
    
    G --> I{Connection Status}
    I -->|Success| J[Fetch Capabilities]
    I -->|Failure| K[Log Error]
    
    J --> L[Store Server Info]
    K --> M[Mark Server Unavailable]
    
    L --> N[Monitor Health]
    M --> N
    
    N --> O{Health Check}
    O -->|Healthy| P[Update Capabilities]
    O -->|Unhealthy| Q[Attempt Reconnect]
    
    Q -->|Success| P
    Q -->|Failure| R[Update Status]
    
    P --> N
    R --> N

The Hub Server actively manages MCP servers through:

1. Configuration-based server initialization
2. Connection and capability discovery
3. Health monitoring and status tracking
4. Automatic reconnection attempts
5. Server state management

Request Handling

sequenceDiagram
    participant C as Client
    participant H as Hub Server
    participant M as MCP Server
    
    Note over C,H: Tool Execution Flow
    C->>H: POST /api/servers/{name}/tools
    H->>H: Validate Request
    H->>H: Check Server Status
    
    alt Server Not Connected
        H-->>C: Error: Server Unavailable
    else Server Connected
        H->>M: Execute Tool
        
        alt Tool Success
            M-->>H: Tool Result
            H-->>C: Success Response
        else Tool Error
            M-->>H: Error Details
            H-->>C: Error Response
        end
    end
    
    Note over C,H: Resource Access Flow
    C->>H: POST /api/servers/{name}/resources
    H->>H: Validate URI
    H->>H: Check Server Status
    
    alt Valid Resource
        H->>M: Request Resource
        M-->>H: Resource Data
        H-->>C: Resource Content
    else Invalid Resource
        H-->>C: 404 Not Found
    end

All client requests follow a standardized flow:

1. Request validation
2. Server status verification
3. Request routing to appropriate MCP server
4. Response handling and error management

Requirements

• Node.js >= 18.0.0

Todo

• [ ] Implement custom marketplace rather than depending on mcp-marketplace

Acknowledgements

• Cline mcp-marketplace - For providing the MCP server marketplace endpoints that power MCP Hub's marketplace integration