This exists to shorten the moment of staring at an empty input box wondering what to type. Based on what the model just answered, it proposes natural follow-ups — "Go deeper," "Give an example," "Summarize as a table" — that the user can send with a tap instead of typing.
The default behavior is: tapping a chip sends that exact phrase as the user's message immediately. You could instead just fill the input box and let the user review or edit it first, but that turns one click into two. Either is fine as long as it's consistent.
Two to four chips is a reasonable range. More than that turns picking one into its own decision (Hick's law), and long phrases wrap onto a second line and look messy — keep them short enough to fit on one.
When to use
Show it right after a response, when several natural next directions exist. Skip it after a question with only one right follow-up, like a yes/no answer.