MessagePack advocated MessagePack RPC, but formulation is stopped and it is not widely used.
I've created gRPC based MessagePack HTTP/2 RPC streaming framework called MagicOnion. gRPC usually communicates with Protocol Buffers using IDL. But MagicOnion uses MessagePack for C# and does not needs IDL. If communicates C# to C#, schemaless(C# classes as schema) is better than IDL.
The StreamJsonRpc library is based on JSON-RPC and includes a pluggable formatter architecture and includes a sample MessagePack plugin.