Obviously you accidentally recreated a language from the 70s :P

(I created a template language for JSON and added branching and conditionals and realized I had a whole programming language. Really proud of my originality until i was reading Ted Nelson's Computer Lib/Dream Machines and found out I reinvented TRAC, and to some extent, XSLT. Anyway LLMs are very good at reasoning about it because it can be constrained by a JSON schema. People who think LLMs only regurgitate haven't given it a fair shot)

FWIW, I think a JSON-based XSLT-like thing sounds far more enjoyable to use than actual XSLT, so I'd encourage you to show it off.