The doorway itself rewards a closer look. It is set in three orders with a pointed arch on the exterior and a flattened segmental arch on the inside, the whole thing cut from local red sandstone, with a draw-bar socket still visible at mid-height. An aumbry, a small rectangular recess built into the wall to hold liturgical vessels, survives below the east window, and a broken stoup, a basin once used to hold holy water, remains partially embedded at the southwest angle of the building. The place is unusual for another reason noted as early as 1841: no saint's name and no saint's day are remembered in connection with it, which is rare for a medieval Irish parish church.

The townland takes its name from the Irish Eanach an Ambrósaigh, meaning the marsh of the Ambroise family, an Anglo-Norman surname, and that layered quality of Gaelic and Norman influence runs through the church's documentary history as well. By 1306 it was already a functioning parish church, valued at 40 shillings per annum in the Papal taxation of that year. In 1418 a pair of papal letters concerning a priest named Richard de More became entangled in questions of noble birth and competing benefices, with the rectory of Annagh changing hands following the deaths of two successive incumbents, one Maurice Fyt and one Maurice O'Cahill. The Earl of Desmond was recorded as the patron of the church in the Desmond Survey, and in 1601 a William Ambrose of Annagh received a royal pardon from Queen Elizabeth I. By 1615 the building was already described as ruinous, its parish served by a Protestant minister named Nathaniell Walkward, valued at just £5. A ringfort survives 35 metres to the south, a reminder that this corner of Kerry was settled and organised long before the church was ever built.

Survey work carried out in 2008 found the ruins in reasonably stable condition, free of ivy, and noted at least twenty-six displaced architectural fragments, most of them lodged into or lying along the partially rebuilt west gable. Several of these dressed red sandstone pieces form parts of window embrasures, and one chamfered fragment, possibly from a string course, had been repurposed as a grave marker near the Gace-Forther tomb. The southern wall survives close to its original height, making it the most legible elevation, and the carved knight panel just inside the doorway remains the most striking single object on the site.