suggestion: Copy for "System Prompt Text" Information bubble

[raverydavis]

Need copy for what is in the information bubble of "System Prompt Text" in Chat Context Definition Notebook (I hope these are all the right terms). I can make suggestions on the copy for now if needed

Illustration

[rhennigan]

@raverydavis suggestions would be welcome. We definitely need something better than the placeholder text that I came up with.