That uncertainty is, in its own way, the most interesting thing about the place. The headland is described as nearly inaccessible, its interior worn down to bare bedrock by centuries of coastal erosion, and what faint traces remain of any human construction are too ambiguous and too dangerous to examine closely. It is the kind of site that sits at the edge of the archaeological record, present enough to note, elusive enough to resist classification.

A promontory fort is a type of defended enclosure in which a headland or coastal spur is cut off on its landward side by a ditch, bank, or wall, leaving the sea cliffs to serve as natural defences on the remaining sides. At Na Grafaí, the signs of exactly such an arrangement are just barely visible. A rock-cut fosse, essentially a defensive ditch carved into the bedrock, and the collapsed, grass-covered remains of what may have been a wall, run across the landward approach. The promontory itself retains a high central spine, but otherwise its interior has eroded featurelessly down to the rock. Shapes that might be collapsed walls are visible on the headland, but the terrain makes any closer investigation impractical and unsafe. A survey by Casey in 2002 recorded the site as a possible rather than confirmed fortification, noting that the surface indications were simply too slight to determine their nature with any confidence. The surrounding landscape offers little shelter; the area is hilly, boggy grazing land, and the headland is overlooked by higher ground both inland and to the west, which would have been a meaningful tactical disadvantage for anyone relying on the site for defence.