This is a wedge tomb, a type of megalithic burial monument built during the late Neolithic and early Bronze Age, typically characterised by a gallery that narrows and lowers toward the east. At Coumaclavlig, that gallery stretches 2.6 metres in length and roughly 1.1 metres in width, with its eastern end sealed by a backstone and its western entrance framed by two jamb-like stones set transversely, leaving an opening of just 0.55 metres. What gives the structure additional interest is the arrangement immediately west of those jambs: two uprights and an almost prostrate slab together suggest a portico, a small forecourt-like antechamber of about 1.1 metres, which would have defined a threshold between the outside world and the burial space beyond.

The tomb's covering stones have survived, if not entirely in their original positions. Two roofstones remain over the gallery; the larger measures 2.65 metres by at least 1.5 metres and is between 12 and 15 centimetres thick, while the smaller, which partly overlaps it near the entrance end, measures 1.3 metres by 0.95 metres. Despite the general collapse, enough survives to read the original design with reasonable confidence. The forest surrounding it was planted in 1991, so the tomb now sits within a relatively young plantation rather than the open upland that would have characterised the landscape for most of its existence. From the slope there are views southward and southeastward down the valley toward Glengarriff Harbour, suggesting the site was not chosen without thought for its setting. What makes Coumaclavlig particularly striking in a wider sense is its company: another wedge tomb lies around 900 metres to the southwest, and a third is visible across the valley approximately 1.4 kilometres to the west-northwest, a quiet cluster of monuments spread across the upper reaches of the same river valley.