Cooperative Nature

[Fult]

«You gain a +2 circumstance bonus to your check when you use the Aid reaction or Assist action (see page 307).»

Fult sees no check in the Assist action sooo Fult should read : «You gain a +2 circumstance bonus to your check when you use the Aid reaction or to your attack when you use the Assist action (see page 307).»

Fult is pernickety today.

[Tzakkesh]

Isn't an attack roll inherently a check against the DC of the target's AC?

As long as it is "roll a D20 and add a modifier from your character sheet (and possibly other in-game bonuses) and compare it to a set number" it is a check.