[cheriot]

That's ideal and needs to be the first approach. In practice, people that communicate all day don't always understand than other jobs require uninterrupted focus. That's why engineers try things like no-meeting-wednesdays and schedule blocks for coding.

I wouldn't use the tool in question, but I relate to the motivation.

[Xylakant]

if you need to use this tool, the uninterrupted focus is most likely already gone, damage done. it's even likely that the person will return once your call is done to interrupt you again.

[mgkimsal]

or.... they'll learn that you prioritize answering calls over f2f, and they'll start calling you all the time. easier to 'avoid' to some degree, but you're just shifting the interruption.

[jmkd]

One thing often overlooked about work interruptions: interrupting one person's flow is usually to aid another's.

So as others have suggested the response can be prioritised according to importance and urgency.

While flow is critical for productive work, it should be directed to the highest priority tasks.

[cmdrfred]

In construction we have a phrase "a dime holding up a dollar". It is up to you to decide if you are a dime or a dollar in each situation.