I'm unclear how the "COMPLETE THE ITEM" challenge is done.
P181 of Pathfinder Unchained.
You have the option to Improvised the task with Use Magic Device
or
Provide the requirements, no roll required.
It looks like attempting Use Magic Device has the possible result of destroying the item or reduce it's cost by 10%.
While actually having the prerequisites and not requiring to roll is a safe bet without reward.
OR
That not needing to roll = Critical success bonus automatically.
So which is it?
