The Harmonised System code - an international product classification, six digits globally and more at national level, that decides which tariff band a thing falls into.
Everything importable has one. The code, not your description of the item, determines the duty rate, whether a permit is needed, and which regulator has to sign it off.
Classifying an item optimistically to get a lower rate is a well-worn move and a bad one: reclassification comes with the duty you avoided plus a penalty, and customs has the goods.
A clearing agent earns their fee here more than anywhere else.