i found the Kaitai toolset (IDE, compiler) to be useful in parsing or "deserialization" for proprietary financial protocols. if you are just reading data (especially in an environment with clients in different languages) it's a strong recommend, however lack of support for "serialization" means that you will still need to roll your own encoders. ultimately we created our own tooling/DSL for encoding as well as generating KSY files to generate clients as part of our builds

edit: i forgot to add - there is an issue for serialization on kaitai github repo for some time [1], with some interesting discussion around the implementation challenges

1. https://github.com/kaitai-io/kaitai_struct/issues/27