Views define, what's shown to the user when the command is executed. The view can be provided at the root of the Command Response using the CommandReponse.view property.
The simplest view one can use is text. Simply set the view property to some text and it will be shown in the Command Bar.
"view": "Ahoy, world!"
Read on about other views that can be used in the Command Response: List, Masonry and Form.