I’m looking for a resource to gently pass to my client to help coach him up. He wrote all the server APIs, I write one of the mobile apps. His APIs are all mass

I’m looking for a resource to gently pass to my client to help coach him up. He wrote all the server APIs, I write one of the mobile apps. His APIs are all massive JSON dumps of columns from the database where most of the fields have no use on mobile. The documentation is an out of date printout of the structures with comments, in Ruby I think. Worse he doesn’t seem to do any data validation, I recently passed an index instead of an id for one field and ended up with tons of test data that’s broken. Not because of a bug in my code mind you, but because I misunderstood the cryptic comment. Lastly, he occasionally asks the mobile apps to do processing of the data that’s more easily and safely done on the server. It’s like he misunderstands the role and value of the server in a client server application. But again he’s my client so I have to be gentle.