protobuf may very well be total overkill. What you wanted to do was strongly type your configuration. What you get is a complete RPC layer.
This might not even be warranted when inter-process communication is a primary concern. After all, there's nothing inherently wrong with using whatever data transfer mechanism your standard lib provides.
It's not just protobuf though. Almost every data format for serializing structured data suffers from pushing a jungle on you when all you asked for was a banana.
The least invasive format I know of is FlatBuffers[0]. Doesn't push RPC on you. Allows you to parse a message even if you do not know this specific message's data structure in advance (like JSON).