[fairenough42]

https://google.aip.dev/ gives lots of advice for structuring a gRPC API. What you say is mostly in line with that, with some exceptions. For example https://google.aip.dev/135 suggests that a delete operation on a resource should normally return google.protobuf.Empty. Of course, this is implicitly a sum type; you either get an empty response or an error message. If you needed to return anything else, you're not just implementing a delete. Two exceptions they call out are soft-deletes (not just a delete...) returning the resource itself, and a delete that's a long-running operation.