The Microsoft Research paper assessing intelligence capability of GPT4 effectively did this. If you just define APIs for the model to use under certain conditions it will write the API call. Once you do that, it's straightforward for a layer on top to detect the API call, actually execute it, and write the result back.

Wish they would have stayed open source, but can understand why they would sell out. There would have been no way they could handle the amount of traffic/need if they would have remained a non-profit. But as someone who works for a non-profit, I don't understand how they legally changed to a for-profit over a weeks time period. 😐