A mod in Hotscreen is only a your_mod.mod.tscn text file : a Godot scene that will be loaded into the game. It's mainly for developers but if you want something simple or only want to edit an existing mod, a powerful AI like chatGPT can create it for you.
There is no API to know ! It's just that the 0.7 contains an example of a mod that use the Bluesky API.