You can use common sense to check it.
With the engine at idle, shine a flash light on it.
It should be spinning true and straight. Compare to other pulleys
for reference. If it is wobbling or fluttering about, I would recommend
changing it. If it starts to make noise, look carefully to see if it has
migrated into the oil pan rearwards.
You should be fine with the one you have.
Dr.D

__________________
Dr.Diesel -
Shop Foreman
Master Guild Mercedes-Benz Technician.

Think the dealer is expensive? Do you know how much it costs to train a dealer tech? Or buy the required MB special tools to have on hand?