Elgato Key Light

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

Requirements

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

Setup

bundle install

Run

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

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).

Add to Claude Desktop or .mcp config

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.

Test via JSON-RPC

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":{}}}