I've been looking at the Friends cantrip, and the more I think about it the less useful it appears.
It appears to be self-defeating: you can gain advantage in a conversation, but they'll know you manipulated them pretty quickly. You might use it to bypass a guard, but they're all too likely to shout “Intruder!” once it wears off. You could use it on a merchant, but they're all too likely to turn adversarial afterwards, leaving you disadvantaged for the entire duration of your stay in town.
You can't use it to help with someone actively hostile to you, such as during an interrogation, eliminating the kinds of uses where it doesn't matter if they catch on after.
So what exactly is Friends for?