Assistant Relay is a Node.js server that exposes the Google Assistant SDK, and CATT as a REST API.
Assistant Relay has a number of endpoints for both Google Assistant and CATT. Simply send Assistant Relay a request to the corresponding endpoint, and it'll do the rest.
Assistant Relay also has support for the Google Home Broadcast command, including single device broadcasts, so you can send audio notifications to your Google Home devices without interrupting any media that might already be playing.
At the time of writing, the Google Assistant SDK does unfortunately have a few restrictions, like the inability to ask it to start Netflix on a certain device or to stream music. For more information, check out the FAQ or ask in our Discord channel