Protobufs (the transfer format of gRPC) include not just a schema, but a transport format that may be more efficient than a serialized POCO. gRPC also allows y

Protobufs (the transfer format of gRPC) include not just a schema, but a transport format that may be more efficient than a serialized POCO. gRPC also allows you to encode communication semantics (i.e. "What does this endpoint want as arguments? What does it return?") and generate both client and server code that complies with (and automatically [de]serializes and validates protobuf data for) those semantics. It's the difference between a schema definition and a schema definition + serialization format + service (not just data) definition/codegen.