Hi! These, along with the instruction-trained gpt-3.5-turbo-instruct, are completion models.
They use the completions endpoint, and a “prompt” parameter instead of a list of messages.
Documentation is in the API reference, a lower legacy section.
Important: the base models will continue and continue writing; they are not trained on emitting a token to end the output. You will need to use a stop sequence, along with max_tokens, and special techniques from when “prompt engineering” meant something.