Similar to Microsoft visio this feature will give users the Ability to make interaction points explaining functionality in the prototype. The user will be able to draw an arrow pointing at the element linking to the dialog box. A dialog box will give user info on functionality or explain Interaction point.
This feature will show in prototype mode and give the option to enable in share prototype mode.

As a user, I can draw an interaction box.
As a user, I can link interaction box to shape/element/ect.
As a user, I can choose to enable this when I share a prototype.