It is true that gRPC tends to implicitly imply Protocol Buffers. It's the only format that is worked on directly by the gRPC team.
However, C#/C++ Bond, C++ FlatBuffers, and Java Avro have some level of code generation support for gRPC. I'm not very familiar with Microsoft's Bond, but it appears to have generics for both the service and structs.
However, C#/C++ Bond, C++ FlatBuffers, and Java Avro have some level of code generation support for gRPC. I'm not very familiar with Microsoft's Bond, but it appears to have generics for both the service and structs.
disclaimer: I'm part of the gRPC team.