The site consists of a single drystone wall, now partially tumbled, enclosing a rectangular field measuring approximately 22 metres on its longer axis. A cashel is simply a stone-walled ringfort, the drystone equivalent of the earthen raths found elsewhere in Ireland, and while circular examples are the norm, this one is conspicuously rectangular, a shape that sits slightly outside the expected pattern.

The enclosure appears on the 1842 Ordnance Survey six-inch map, where hachuring suggests the outline of an earlier structure beneath or coinciding with the present wall line, and it reappears on the 1915 edition marked with a solid line. By 1996, when it was formally listed in the Record of Monuments and Places, it was categorised as a rectangular enclosure rather than a conventional ringfort, reflecting some uncertainty about how best to classify it. That uncertainty has not entirely dissolved. Rectangular cashels are documented elsewhere in the Burren, the limestone plateau of which this part of Clare forms a part, and researchers including Comber and Bowmer have examined the type in publications from 2010 and 2019. The Formoyle site is considered a possible addition to that category, though the qualification matters: the wall's partial collapse and the layering of different periods of use make a definitive reading difficult.

The site sits on a moderately steep slope facing east-north-east, roughly 360 metres from the Caher River. That orientation and position, looking out over a river valley from a defended elevated point, is consistent with the kind of early medieval farmstead these enclosures typically represent, though nothing in the visible remains resolves exactly when it was built or by whom.