Function baseRT_grammar_create_from_schema 

pub unsafe extern "C" fn baseRT_grammar_create_from_schema(
    model: baseRT_model_t,
    json_schema: *const c_char,
) -> *mut c_void

Create a grammar from a JSON Schema (converted to GBNF internally); NULL on error. Used to validate that a codec’s tool-call grammar compiles in the engine (the runtime constrained-decode path).