As the name implies, the Exegetes were called upon to contribute their knowledge and experience on religious matters when the occasion called for it. Although the office is old, it is not certain that they were considered priests before the Hellenistic period. However, they always had some things in common as they shared a deep knowledge of sacred subjects and Mysteries. There were three Exegetes in the Athenian state, but only the Exegetes of the Eumolpidae were related to the Eleusinian Mysteries. Incidentally, they were also three in number.

The right of explanation belonged exclusively to the Eumolpidae. Still, it does not seem that there was a dedicated and official member of the family who took on this role whenever the occasion required it. The hierophant or any other priest of the genos could explain, as long as he enjoyed the general respect for knowing the tradition. Gradually, the members of the genus who proved to be more effective would be called upon to contribute their knowledge on a more permanent basis. At the same time, the growing popularity of the Mysteries and the participation of mystai from every corner of the Greek (and Roman) world made the need for homogeneous teaching of the patria. The Eumolpidae responded to the challenge by selecting specific members to take on exegetes' roles and dedicate themselves exclusively to resolving issues regarding the Mysteries. An inscription of the middle of the second century BCE stipulates that the Exegetes should be available from the first day of the month of Boedromion to aid anyone interested in participating in the upcoming rituals.

In 67 BCE Cicero was looking for a copy of the ancestral beliefs of the Eumolpidae. It is unclear whether there was an official record of these ancient laws or whether Cicero had in mind a text written by priests and scholars interested in the traditions of the Eleusinian Mysteries. It seems, however, that there was some attempt to codify the patria because from the second century CE, the references to invocations to Exegetes cease and the issues that arise are resolved by the hierophants.