If you tell it to return only JSON, it will. Then you can parse that response and pretend you actually made an API.
For example, with my latest GPT adventure (https://socialpostgpt-client.fly.dev/), I'm asking for a search query which I can use to find stock photos on Pexels.
You must respond ONLY with JSON that looks like this: {"query": "some search query" } and no extra text.
Generate a search query that can be typed into stock photo websites that will find photos that fit the following content: "{some user input}"