Imagine you’re at a very special fast food restaurant where the kitchen is capable of producing anything you want. Your order can have any ingredient and can come out looking any way you can imagine. You are very hungry. But you have to follow one rule: if you don’t get exactly what you want, you can’t just accept it. You have to send it back for the kitchen to produce it again. (And no, you can’t go make it yourself.)
What is the best way to order your food?
Would you email your order to the order-taker?
Would you go to the drive-thru window and tell the order-taker through the intercom?
Would you go to the counter and tell the order-taker in person?
Would you go into the kitchen with the order-taker and show the cooks what you want?
You can point to the ingredients and rapidly iterate how it is presented. In Scrum, the Product Owner is not just the order-taker. They are a stand-in for you, the customer. You are supposed to be of the same mind.