I looked into Clojure with Antlr, and there seems to be a lot of barriers

I have not tried that, yet, but I'm interested to know what you are thinking of doing with such a capability.

In the short term I want to be able to compare C# classes against an openapi spec as well as a database schema. All of these are different representations of the same data model

My preference would be that there's a single source of truth for all of those things rather than having to compare, but that would be a longer term effort