The main thing that Cap'n Proto PRC really requires about the serialization is that object references are a first-class type. That is, when you make an RPC, the

The main thing that Cap'n Proto PRC really requires about the serialization is that object references are a first-class type. That is, when you make an RPC, the parameters or results can contain references to new, remote RPC objects. Upon receiving such a reference, that object is now callable. Making this work nicely requires some integration between the serialization layer and the RPC layer, though it's certainly possible to imagine Protobuf being extended with some sort of hooks for this.