I like that JSON parsing libraries (Serde etc.) allow you to validate nullability constraints at parse-time. Protobuf's deliberate lack of support for required fields means that either you kick that down to every callsite, or you need to build another parsing layer on top of the generated protobuf code.

Now, there is a serde_protobuf (I haven't used it) that I assume allows you to enforce nullability constraints but one of the article's points is that you can use the generated code directly and:

> No manual validation. No JSON parsing. No risk of type errors.

But this is not true—nullability errors are type errors. Manual validation is still required (except you should parse, not validate) to make sure that all of the fields your app expects are there in the response. And "manual" validation (again, parse don't validate) is not necessary with any good JSON parsing library, the library handles it.