Building API integrations in Mendix is tedious.
not being able to see the errors from the endpoint makes it harder.
I'm often not sure if something is going wrong with my call, or my mapping, my token or something else random (like validations on the receiving end).
I currently rebuild all my calls in postman, so that I can troubleshoot different scenarios.
Debugging in Mendix
debugging in postman
A better rest client is in development, you can try it in Mendix 10.