MCP-Hub

A Go-based hub that aggregates multiple MCP (Model Context Protocol) servers and exposes their tools through a unified HTTP API.

Features

• Standard MCP Protocol: Full support for MCP 2024-11-05 specification
• Multiple Transport Types:
  • Stdio: For local MCP servers (Node.js, Python, etc.)
  • HTTP/SSE: For remote MCP servers
• Configuration-Based: JSON configuration compatible with Cursor/VSCode format
• Docker-Ready: Easy deployment in containers with volume mounts
• Tool Aggregation: Combine tools from multiple MCP servers in one place
• HTTP API: RESTful endpoints for tool discovery and execution

Quick Start

1. Build

cd cmd/mcp-hub
go build -o ../../mcp-hub

2. Create Configuration

Create a `config.json` file (see `config.example.json` for a template):

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
    },
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "${GITHUB_TOKEN}"
      }
    }
  }
}

3. Run

# Using default config.json
./mcp-hub

# Or specify a config file
./mcp-hub --config /path/to/config.json

Notes:

• The HTTP listen address can be overridden with the `MCP_HUB_PORT` or `PORT` environment variable. If the value contains a colon it is treated as a full address (e.g. `0.0.0.0:8080`), otherwise it is treated as a port and is prefixed with a colon.
• The binary accepts a `--config` flag (default: `config.json`).

4. Use the API

List all available tools:

curl http://localhost:8080/mcp/tools

Execute a tool:

curl -X POST http://localhost:8080/mcp/execute \
  -H 'Content-Type: application/json' \
  -d '{
    "plugin_id": "filesystem",
    "tool_name": "read_file",
    "arguments": {"path": "/tmp/test.txt"}
  }'

List connected servers:

curl http://localhost:8080/mcp/servers

Configuration Format

The configuration file uses the standard `mcpServers` format compatible with Cursor, VSCode, and Claude Desktop.

Stdio Servers (Local)

For MCP servers that run as local processes:

{
  "mcpServers": {
    "server-name": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-package"],
      "env": {
        "API_KEY": "${YOUR_API_KEY}"
      },
      "timeout": 30
    }
  }
}

Fields:

• `command`: Executable to run (required)
• `args`: Command line arguments (optional)
• `env`: Environment variables (optional, supports `${VAR}` expansion)
• `timeout`: Request timeout in seconds (optional, default: 30)
• `disabled`: Set to `true` to disable a server (optional)

HTTP Servers (Remote)

For MCP servers accessible via HTTP:

{
  "mcpServers": {
    "remote-server": {
      "type": "http",
      "url": "http://localhost:3000/mcp",
      "headers": {
        "Authorization": "Bearer ${API_TOKEN}"
      },
      "timeout": 45
    }
  }
}

Fields:

• `type`: Set to `"http"` for HTTP transport (or auto-detected from `url`)
• `url`: HTTP endpoint URL (required)
• `headers`: HTTP headers to include (optional, supports `${VAR}` expansion)
• `timeout`: Request timeout in seconds (optional, default: 30)

Environment Variables

Environment variables in the configuration are expanded using `${VAR_NAME}` syntax. For example:

{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "${GITHUB_TOKEN}"
      }
    }
  }
}

Then run:

GITHUB_TOKEN=your_token_here ./mcp-hub

Docker Deployment

Image Variants

The repository provides two Docker image variants, optimized for different use cases:

1. Standard Image (`Dockerfile` / `mcp-hub:latest`)

• Size: ~47MB
• Includes: Alpine Linux + Docker CLI + mcp-hub binary
• Use when: You need Docker transport for running MCP servers in containers, or mixed transports
• Best for: Production deployments with container-based MCP servers

2. Local MCP Servers Image (`Dockerfile.local` / `mcp-hub:local`)

• Size: ~800MB
• Includes: Node.js 20, Python 3, uv, curl, git, and mcp-hub binary
• Use when: You want to run local stdio-based MCP servers (Node.js, Python) in the same container
• Best for: Self-contained deployments where the hub and all MCP servers run together

Build Docker Image

To build a specific image locally:

# Standard image (with Docker CLI)
docker build -t mcp-hub:latest .

# Local MCP servers image (with Node.js, Python, uv)
docker build -f Dockerfile.local -t mcp-hub:local .

Run with Docker

# Create a config directory
mkdir -p config

# Put your config.json in the config directory
cp config.json config/

# Run the container
docker run -d \
  -p 8080:8080 \
  -v $(pwd)/config:/config:ro \
  -e GITHUB_TOKEN=${GITHUB_TOKEN} \
  mcp-hub

Docker Compose

version: '3.8'
services:
  mcp-hub:
    build: .
    ports:
      - "8080:8080"
    volumes:
      - ./config:/config:ro
      - ./plugins:/plugins:ro  # Optional: mount custom plugins
    environment:
      - GITHUB_TOKEN=${GITHUB_TOKEN}
      - BRAVE_API_KEY=${BRAVE_API_KEY}

HTTP API Reference

GET /mcp/tools

List all available tools from all connected MCP servers.

Response:

[
  {
    "id": "read_file",
    "name": "read_file",
    "description": "Read contents of a file",
    "plugin_id": "filesystem"
  }
]

POST /mcp/execute

Execute a tool on a specific MCP server.

Request:

{
  "plugin_id": "filesystem",
  "tool_name": "read_file",
  "arguments": {
    "path": "/tmp/test.txt"
  }
}

Response:

MCP tool call result (format depends on the tool)

GET /mcp/servers

List all connected MCP servers.

Response:

{
  "servers": ["filesystem", "github", "brave-search"]
}

GET /mcp/stream

Server-Sent Events stream of tool registry updates (for real-time tool discovery).

Examples

Example 1: Using Official MCP Servers

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/home/user/documents"]
    },
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "${GITHUB_TOKEN}"
      }
    },
    "brave-search": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-brave-search"],
      "env": {
        "BRAVE_API_KEY": "${BRAVE_API_KEY}"
      }
    }
  }
}

Example 2: Custom Python MCP Server

{
  "mcpServers": {
    "custom-tools": {
      "command": "python3",
      "args": ["/app/plugins/custom_mcp_server.py"]
    }
  }
}

Example 3: Mixed Local and Remote Servers

{
  "mcpServers": {
    "local-filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/data"]
    },
    "remote-api": {
      "type": "http",
      "url": "https://api.example.com/mcp",
      "headers": {
        "Authorization": "Bearer ${API_TOKEN}"
      }
    }
  }
}

Development

Project Structure

.
├── cmd/
│   └── mcp-hub/
│       └── main.go           # Entry point
├── internal/
│   ├── config/
│   │   └── config.go         # Configuration parsing
│   ├── mcp/
│   │   └── protocol.go       # MCP protocol structures
│   ├── plugin/
│   │   └── manager.go        # Server management
│   ├── registry/
│   │   └── registry.go       # Tool registry
│   ├── server/
│   │   └── server.go         # HTTP server
│   └── transport/
│       ├── transport.go      # Transport interface
│       ├── stdio.go          # Stdio transport
│       └── http.go           # HTTP transport
├── config.example.json       # Example configuration
└── README.md

Adding New Transport Types

Implement the `Transport` interface in `internal/transport/`:

type Transport interface {
    Start(ctx context.Context) error
    SendRequest(ctx context.Context, req interface{}) (json.RawMessage, error)
    SendNotification(ctx context.Context, notification interface{}) error
    Close() error
    IsConnected() bool
}

Troubleshooting

Server fails to start

Check logs for specific error messages. Common issues:

• Missing `npx` or `python3` in PATH
• Invalid MCP server package names
• Missing environment variables
• Incorrect file paths in configuration

Tool execution fails

• Verify the MCP server is properly initialized (check `/mcp/servers`)
• Ensure tool arguments match the expected schema
• Check server logs (stderr output is visible in hub logs)

Timeout errors

Increase the `timeout` value in server configuration:

{
  "mcpServers": {
    "slow-server": {
      "command": "...",
      "timeout": 120
    }
  }
}

License

MIT

Docker Servers (Containerized)

For MCP servers running in Docker containers:

{
  "mcpServers": {
    "containerized-server": {
      "type": "docker",
      "image": "my-mcp-server:latest",
      "args": ["--option", "value"],
      "env": {
        "API_KEY": "${YOUR_API_KEY}"
      },
      "volumes": {
        "/host/path": "/container/path",
        "${HOME}/data": "/data"
      },
      "network": "mcp-network",
      "timeout": 60
    }
  }
}

Fields:

• `type`: Set to `"docker"` for Docker transport (or auto-detected from `image`)
• `image`: Docker image name (required)
• `args`: Command arguments to pass to container entrypoint (optional)
• `env`: Environment variables (optional, supports `${VAR}` expansion)
• `volumes`: Volume mounts as `host:container` mappings (optional, supports `${VAR}` expansion)
• `network`: Docker network to connect to (optional)
• `timeout`: Request timeout in seconds (optional, default: 30)

Benefits of Docker Transport:

• No need to install Node.js, Python, or other runtimes on the hub host
• Isolated dependencies per MCP server
• Easy version management with Docker tags
• Consistent environment across deployments

Building Docker Images for MCP Servers

You can containerize any MCP server to avoid installing its dependencies on the hub host.

Example: Dockerizing a Python MCP Server

Dockerfile:

FROM python:3.11-slim

WORKDIR /app

# Install dependencies
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy MCP server code
COPY mcp_server.py .

# Run as non-root user
RUN useradd -m -u 1000 mcpuser && chown -R mcpuser:mcpuser /app
USER mcpuser

# The server should read from stdin and write to stdout
ENTRYPOINT ["python", "-u", "mcp_server.py"]

Build and use:

# Build the image
docker build -t my-mcp-server:latest .

# Add to config.json
{
  "mcpServers": {
    "my-server": {
      "image": "my-mcp-server:latest"
    }
  }
}

Example: Dockerizing a Node.js MCP Server

Dockerfile:

FROM node:20-alpine

WORKDIR /app

# Install dependencies
COPY package*.json ./
RUN npm ci --production

# Copy server code
COPY . .

# Run as non-root user
RUN addgroup -g 1000 mcpuser && \
    adduser -D -u 1000 -G mcpuser mcpuser && \
    chown -R mcpuser:mcpuser /app
USER mcpuser

ENTRYPOINT ["node", "server.js"]

Important Notes for Docker MCP Servers

1. Use `-i` flag: The hub runs containers with `docker run -i` for interactive stdin/stdout

2. Unbuffered output: Ensure your server outputs are unbuffered (use `python -u` or `flush()`)

3. Stdin/Stdout only: The MCP protocol uses stdin for input and stdout for output

4. Stderr for logs: Use stderr for logging (visible in hub logs)

5. Cleanup: Containers are run with `--rm` for automatic cleanup

Pre-built MCP Server Images

Create a registry of Docker images for common MCP servers:

# Example: Build an echo server image
cd examples/plugins
cat > Dockerfile  config.json << 'JSON'
{
  "mcpServers": {
    "echo": {
      "image": "mcp-echo:latest"
    },
    "custom-tools": {
      "image": "my-mcp-server:v1.0",
      "env": {
        "API_KEY": "${MY_API_KEY}"
      },
      "volumes": {
        "/host/data": "/data"
      }
    }
  }
}
JSON

# 4. Run the hub
MY_API_KEY=secret123 ./mcp-hub --config config.json

This setup gives you:

• ✨ No runtime dependencies on the hub host
• ✨ Isolated environments for each MCP server
• ✨ Easy updates by changing Docker image tags
• ✨ Reproducible deployments

Containerized Deployment

The mcp-hub itself can run in a Docker container. See DOCKER_DEPLOYMENT.md for complete deployment guide.

Quick Docker Deploy

# Build the image
docker build -t mcp-hub:latest .

# Run with your config
docker run -d \
  --name mcp-hub \
  -p 8080:8080 \
  -v $(pwd)/config.json:/app/config.json:ro \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e GITHUB_TOKEN=${GITHUB_TOKEN} \
  mcp-hub:latest

Or use Docker Compose

docker-compose up -d

Image Sizes:

• Standard (with Docker CLI): ~47MB
• Minimal (stdio/HTTP only): ~6MB

Environment variables are automatically passed through and expanded in your configuration.

Config File Watching

The MCP Hub automatically watches the configuration file for changes and updates the registry accordingly. When you modify `config.json`, the hub will:

• Add new servers: Automatically start any newly added MCP servers
• Remove servers: Stop servers that are removed from config or disabled
• Reload servers: Restart servers whose configuration has changed
• Update registry: Keep the tool registry in sync with active servers

How It Works

The watcher uses `fsnotify` to monitor the config file for write events. When changes are detected:

1. The new config is loaded and validated

2. Changes are compared with the previous configuration

3. Appropriate actions are taken (start/stop/reload servers)

4. The registry is automatically updated

5. Changes are logged for visibility

Debouncing

To avoid processing rapid successive changes (e.g., when editors write multiple times), the watcher includes a 500ms debounce delay. This ensures the config is only reloaded once after you finish editing.

Example

# Start mcp-hub
./mcp-hub --config=config.json

# In another terminal, edit config.json
vim config.json

# The hub will automatically detect changes and log:
# "config file changed, reloading..."
# "adding server: new-server"
# "loaded MCP server: new-server (stdio transport)"

Error Handling

If the new config contains errors:

• Invalid JSON: Changes are rejected, hub continues with previous config
• Missing required fields: Changes are rejected with validation error
• Server startup failures: Logged as warnings, other servers continue running