One example of a 500 error is a null pointer error. Was it a bad request or a logic error? One is your problem the other is not. Just returning a 400 hides t

One example of a 500 error is a null pointer error. Was it a bad request or a logic error? One is your problem the other is not. Just returning a 400 hides that issue. Validating the payload before processing it simplifies the issue for everyone involved. A 500 error should be your problem with a stack trace in the log. A 400 error should provide enough description to tell the user it's theirs and how to fix it. Just marking recoding a 500 to a 400 because of a null pointer error would get noticed on a code review and marked up on a code review.