Bulwark, damaging effects and ambiguity

[Exocist]

What constitutes a damaging effect for the purpose of bulwark? Is it any effect that has the potential to deal damage, or does it need to be one that you can feasibly "avoid".

For instance, engulf does damage on a failed save, does bulwark apply?

Swallow whole does as well, does bulwark apply?

Trip has the potential to do damage (if the opponent crits) does bulwark apply?

[Cordell Kintner]

It should be fixed to only designate Area effects, because that's what it sounds like it's implying. Currently, RAW I would say yes to all but Trip.