The ruin is recorded as a monument, which means it has been identified and catalogued as part of the archaeological landscape, but the details that would allow a curious visitor or researcher to make sense of what they are looking at remain largely out of reach.

Annagh is a townland name derived from the Irish "eanach", meaning a marsh or watery place, and such names across Mayo frequently mark early ecclesiastical settlements, where monks and later medieval communities sought out liminal, slightly isolated ground. Ruined churches of this kind can date from anywhere between the early medieval period and the post-Reformation centuries, and without excavation records, documentary sources, or standing fabric to analyse closely, pinning down a foundation date is difficult. What survives at Annagh has not yet been described in any detail that is publicly available, which places it in an unusual category: a protected monument whose story, for now, belongs more to the landscape than to the written record.