OpenAtlas

I looked into flask-restful. It is not complicated and quite intuitive. Right now, our API can quite the same but flask-restful is way easier to read.
One major problem I found is, that the flask-restful package alone is not compatable with swagger automatic annotation. For this we need another package named _flask-restful-swagger_ which is not a Debian package. We also can you _flask-restx_ which has the swagger annotation included, but again, no Debian package.

I will complete the transformation to restful anyway, because it is easier to read and maybe I find new way to make the API request faster. How we cope with swagger, besides manual manipulation, I don't know.

I'm no expert there but what about python3-flasgger? It's a Debian package and sounds promising:

Flasgger is a Flask extension to extract OpenAPI-Specification from all Flask views registered in your API. It also comes with SwaggerUI embedded so you can access http://localhost:5000/apidocs and visualize and interact with your API resources. It also provides validation of the incoming data, using the same specification it can validates if the data received as a POST, PUT, PATCH is valid against the schema defined using YAML, Python dictionaries or Marshmallow Schemas. Flasgger can work with simple function views or MethodViews using docstring as specification, or using @swag_from decorator to get specification from YAML or dict and also provides SwaggerView which can use Marshmallow Schemas as specification.

This article shows an example how to use it: https://kanoki.org/2020/07/18/python-api-documentation-using-flask-swagger/

As usual, you save the day or night. Thank you! This looks very promising.