I have a form where I would like the user to enter a response or query, and have another field populated using AI. 

For example, user  enters Field 1, AI populates Field 2 in response. I want to be able to wrap some additional instruction text around the query (e.g. Answer in less than 250 characters).

The user should not see the additional instruction text.

Field 1 : The car is a 1998 Ford Focus

What gets passed to ChatGPT : "Provide some history about automobiles. Answer in less than 250 characters:" $(zf:Field 1)

ChatGPT returns the response which is added in Field 2.

Field 2 : The 1998 Ford Focus debuted Ford’s New Edge design, offered superb handling via Control Blade rear suspension, and came in hatch, saloon, and estate forms. It won 1999 European Car of the Year and redefined the small family car segment.

How can I do this in Forms?t