Do Officers Have a Legal Responsibilities to Argue Reasonable Suspicion?

Do police officers have a legal responsibility to articulate their reasonable suspicion that is behind their detention? If so, when do they have to do that? And then related, if a police officer comes up on someone who is actually totally innocent, isn't the officer going to be able to solicit greater cooperation by articulating the reasonable suspicion? So I'm interested in sort of the legal aspect of it but also just on the ground practical aspect of an officer explaining why they're doing what they're doing.