Understand the distinction
Clarity grading considers inclusions and blemishes under defined examination conditions. Eye-clean is an informal description of whether characteristics are visible without magnification, and sellers may use different viewing conditions.
Agree how to judge it
Inspect the stone at a realistic distance and size. Position, contrast, cut and lighting affect visibility. A characteristic can also deserve a durability assessment even when it is not obvious to the naked eye. Ask for the actual stone's images and report.
Sources and further reading
This English edition draws on the source material referenced below.