Are you available for an audio/video call?
Before initiating an audio/video call, I usually send the person a brief chat message asking if they are available/is now a good time for a call.
It would be nice to have some kind of automated feature that sends the intended call recipient a simple ping message indicating that "Jimmy is requesting an audio/video call-is now a good time?"
The responder could click a simple choice of replies such as
"Sure thing!" or "give me 5 minutes"