I wanted to integrate MessagePack with my library which is an Http client for .NET (FluentlyHttpClient).

It uses MediaTypeFormatter for content negotiation, which is very similar to AspNetCore formatters (or even more similar to WebApi formatters), so its a very simple class but might be nice to have it installable for consumers. Are you willing to have a library for it, similar to your own AspnetCore? I can provide you the class.

Thanks!