elgato-key-light-mcp

A Ruby MCP server to control your Elgato Key Light via stdio.

• Ruby 4.0.2
• Bundler
• Elgato Key Light on your local network

bundle install

bundle exec ruby stdio_server.rb

Set the light host if different from the default (192.168.100.13:9123):

ELGATO_LIGHT_HOST=192.168.1.50:9123 bundle exec ruby stdio_server.rb

docker build -t elgato-mcp .
docker run -i --rm elgato-mcp

> macOS limitation: Docker Desktop on Mac does not support --network host, so containers cannot reach LAN devices like the Elgato Key Light. On macOS, skip Docker and connect the MCP server directly (see below).

On macOS, run the server directly with Ruby. Edit ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "elgato-key-light": {
      "command": "/bin/bash",
      "args": ["-c", "cd /path/to/ruby-mcp-el-gato/stdio_server.rb && exec /path/to/bundle exec ruby stdio_server.rb"]
    }
  }
}

Find your bundle path with which bundle.

Control the light:

{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"elgato_key_light_control_tool","arguments":{"on":1,"brightness":50,"temperature":150}}}

Get current state:

{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"elgato_key_light_status_tool","arguments":{}}}