Welcome to our community. I am so pleased to hear that you have been using OpenEMR actively!
As far as an API, this is an area where we would appreciate collaboration. While we have no formal API at this time, it is very possible to meet the API spec you have listed (or one that is similar).
Someone recently asked about an API here: How to use OpenEMR api - there is some good information in that thread, including a link to a previous API that can be used as inspiration.
If you and/or your state is interested, we would love to collaborate to make an API a shining feature of our software. While I’m not sure how many resources would be working on it, I can say that such a project could be completed in a handful of months as a rough estimate.
OpenEMR Project Administrator