The matchmaker supports two subprotocols - JSON and FlatBuffer (aka 'fbs') that define the encoding that is used when sending and receiving messages between the client and the matchmaker. Both protocols describe the exact same data and API, but you may find it easier to integrate one rather than the other.
JSON is the easiest choice for most cases, and can be viewed in the Messages guide.
For the Flatbuffer schema files, please contact us.
The FlatBuffer definitions for the protocol exist can be used to generate source code via the
flatc binary, e.g.
flatc -o generated/cpp --cpp api/protocol/*.fbs will generate C++ source code suitable for encoding and decoding FlatBuffer messages.