- ChatGPT has a system prompt that tells the AI it is ChatGPT and the model it is based on.
- The API requires you to write your own system prompt, which can also be “You are ChatGPT, a large language model by OpenAI…” - or can actually be the way you want your AI to behave.
- ChatGPT has a conversation management system that will pass recent relevant chat back to the AI so it can see what you were recently discussing.
- The API requires you to write the conversation management system yourself to allow the AI to see prior conversation besides just the latest input if you want this chat behavior.
- ChatGPT has an undisclosed “temperature” parameter, which controls how creative or unpredictable the generation of words is;
- In the API, you will likely want temperature 0.5 for most uses, high enough that it doesn’t always give the same answer, but low enough it isn’t completely improvisational.
With identical model, identical system prompt, and identical user input, you will get the same output from the API. Your conversation history can be even better than ChatGPT after many turns if you want to pay the extra amount for submitting maximum chat possible along with every new question.