"Needed" was correct, but detailing the matter would lead to biases. Nigredo could always explain after the fact.

"Yes," he answered quietly. The next words came like a pulse, something delicate and exacting in their execution. "I need you to walk the entire length of the cafeteria while holding your tray high above your head."

Once again, if the power went accordingly, the recipient would hear a familiar voice, understand the context, and follow through without hesitation. It was a cumbersome task, admittedly, but it should suffice as evidence.