The suggestion to modify description_for_model with something like transforms it into text… seems to have done the trick with my plugin passing source code.
Still need a few more days of testing to see if stands the test of time but looks promising.
“description_for_model”: “Validate Prolog code generated by ChatGPT using SWI-Prolog and return results, success or errors. Transform Prolog code in prompt to application/json before sending to plugin.”,