Commercial use of LLMs is one of those spaces a startup probably needs more than skating ahead of the incumbents on the incumbents' “missing” features as startup value prop. Even if the startup has a year or two head start, it may find its beta “OBE” (overcome by events):
https://dottxt.co
That said, Outline has been making this concept portable for a long time, it's the langchain the community deserves:
https://outlines-dev.github.io/outlines/cookbook/