I don't buy this, you have to plan the versions of your "api" if I'm going to change a field into a required field I have to have a plan for clients who don't s

I don't buy this, you have to plan the versions of your "api" if I'm going to change a field into a required field I have to have a plan for clients who don't supply it. You skip all the business and validation logic with direct db access. As for error codes, it doesn't seem non trivial to explain why your validation failed.