Court tombs are among the oldest megalithic monuments in Ireland, typically consisting of a stone-built burial gallery preceded by an unroofed semicircular or oval forecourt where ritual activity is thought to have taken place. The example at Shasgar is modest but structurally legible: an oval cairn, the mound of stones heaped over the whole construction, measuring roughly 17 metres east to west and 12 metres north to south, rising to a maximum height of about 2 metres.

Within the cairn sits a single unsegmented chamber, that is, one long gallery without internal dividing stones, running approximately 7 metres east to west and tapering from around 2.2 metres wide at the western end to 1.5 metres. The entrance, just 0.75 metres wide, is flanked by upright stones called orthostats standing 0.9 metres high, and traces of an oval court roughly 8 metres across survive to the west of the entrance. The roofless condition of the chamber is common among monuments of this age; the great capstones, if they ever existed here, are long gone. Ruaidhrí de Valera and Seán Ó Nualláin documented the site in their 1972 survey of megalithic tombs across the Irish midlands and west, which remains a foundational reference for monuments of this type. The positioning of the tomb at a plateau edge, with open air to the east and a cliff immediately below, gives the site a quality that is hard to attribute to accident, suggesting its builders were attentive not just to the practicalities of construction but to the character of the landscape around them.