The name "Agathangelos" (which in Greek appropriately means "good news") is probably fictional, even though the writer introduces himself in the Prologue as a man from the great city of Rome who is well versed in literary skills and knows several languages. The Prologue also tells us that Agathangelos was an eyewitness to the events he describes. It is unlikely that this is true, especially because some of the words he uses are taken directly from the life of Mesrop Mashtots written by that great monk's student, Koriun (about which you can read in the first volume of this series).
Scholars disagree over how much Agathangelos's history can be taken at face-value. After all, he wrote his book in 460 (Tiridates is believed by Armenians to have converted in 301), and much of his story has elements of hagiography that lead one to wonder whether the events ever happened. But even skeptics acknowledge that Gregory was a real person with considerable ecclesiastical influence in Armenia—the signature of his son and successor Aristakes can be found among those ratifying the Council of Nicaea in 325. And even if we can document little about the man, his pre-eminence among Armenia's heroes of the faith is unassailable.