There is a very specific way to provide the past turns of what the assistant wrote to emit a function call, and then the return value that is placed, to then have the AI answer using the function information it obtained.
It is then up to you how long you want to have function calls remain part of the chat history, if you’d want to expire them faster than the rest of the surrounding chat. You can have the type of function inform the expiration you program. Most assistant/function exchanges are somewhat short compared to full AI responses to a user.