Good question. I'm driving mostly off of my own use cases currently, so AWS SDK/CLI/Terraform compatibility. Response formats, codes, messages are best effort, there's a little work to be done there still. There's some gaps around request validation still too.
The idea is to build up a good suite of integration/regression tests as cases are identified by myself or the community (if there is one) through development.
You can instal the web app to the home screen on IOS so far, it's similar experience. Let me know if you need a guidance to do that, it takes 1 minute.