What should I look at to decide whether to wear it alone or as an inner layer?

"Sheer" refers to a state where light passes through to some extent, showing what is underneath. This top is made of a ribbed jersey blending cotton and nylon, and by using high-twist yarn with tightly twisted threads, that sheer quality remains between the knits^[1].

Tightly twisted threads tend to cling less to the body as they gain elasticity rather than stretching smoothly along the surface, and ribbed knit stretches because it is knit with vertical ridges. However, this top has a slim fit, creating a silhouette that reveals the body line^[2]. Because it is a garment where both sheer see-through quality and body lines are visible, wearing it alone reveals both as they are, and wearing it under a jacket or shirt reveals them only as much as the outer layer is open. The brand has not specified whether it recommends wearing this top alone or as an inner layer.

hmmm, since it is a knit that leaves the sheer see-through quality intact instead of eliminating it, whether to cover it or reveal it reads as a choice left to the wearer.