As far as I can tell you won't be able to use the approach proposed here to create a character matching your above description unless every element of it is encoded in the guiding grammar (including the possibility for the character to have middle ages-relevant weapons, and the anthropomorphic vegetables).

At which point, again I have to ask: what do you need the LLM for? You've already done all the hard work by hand and the LLM is only adding some extraneous natural language parsing on top.

Plus, if you already have the grammar that can cover the anthropomorphic vegetable world it's only a bit more work to use it to parse such natural language requests, anyway.

I think people forget that grammars were the staple for parsing natural language and stuffing it into structured form for a very long time before LLMs, and they still mostly are.

The point is that if you have structure, someone has to hand-craft that structure. Frex, if you have a language with a compiler, someone has to write the compiler. Then, if you want to make some unstructured text conform to your hand-crafted structure, you can only do that to the extent that the unstructured text itself is made up of elements of the structured form. If you have a grammar for frogs and blueberries, and write a poem about the dawn and foxes, you can't use the former to structure the latter, no matter what you do, and LLMs won't make this happen magickally, either.

Essentially, your grammar is a type and any unstructured text you want to convert to a structure with your grammar must be a value that you can cast to that type.

>> I wasn't talking about deterministic Vs nondeterministic.

Then what? What do you mean by "random string"?