Lemmy API: How to obtain the community ID

I want to write a simple Lemmy Command line client that posts to a community.

There is https://join-lemmy.org/api/interfaces/CreatePost.html but it expects a community ID community_id, I would have expected that I can get the community ID by community name / or URL but GetCommunity does not seem to offer this https://join-lemmy.org/api/interfaces/GetCommunity.html#id

Any ideas?