There seems to be similar question Upload object with REST API does not work. Still some questions about this answer to 6211. If id needs to be a hash from body I can not use e.g. postman for testing? POST request needs to be done by coding if body changes. Is that really so that parent objects need also to be updated when posting a new child object? In my opinion this should be taken care by the framework. Makes REST api otherwise a little bit difficult to use without knowing quite much about the structure of the model on server side. Am I totally wrong in my understanding?