Earlier quoted context omitted.
I think he only had GET /door/toggle, which cannot be idempotent.
He mentions later in the thread that he doesn't have a sensor to indicate door position, which is going to kill this project and absolutely prevents an idempotent approach. There are a bunch of ways to approach this, most of which are patented by Chamberlain, which is the specific reason you don't find many garage automation solutions sold as a bundle in the US. Typical bolt-on solutions would be a range finder point…
Range finder seems like the best idea. I was thinking of mounting it on the door motor and pointing horizontally down the track at a reflector attached to the chain/handle.
I love the idea of putting a D1 in the car. Thanks for the link!