What common mistake do developers make with Resource endpoints, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with Resource endpoints, why does the mistake cause problems, and what is the safer approach? One recurring problem with resource endpoints is applying it without understanding the boundary it protects. Returning HTML error pages from a JSON API without considering content negotiation and client expectations. In addition, REST-style endpoints commonly use nouns for resources and HTTP verbs to represent operations. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.