This is the result of me flailing around at the API endpoints I could find in the logs from the official DTRPG app. This should (I think) be enough to recreate all the functionality in the app.
The reason for putting this together is so I can (hopefully) create a more robust library app with some better features. But more on that another time.
I'm uploading this here both for my tracking and in the event that it's useful to someone else.
These MD files were created with Obsidian.