are prophecies a reliable source?

as an apprentice of magic id like to know if this is a sound method of citing sources. ive had to write so many essays on my foresight and prophecy readings that my quill is growing an indent of my hand. i dont want to explain how i know, i just do, why do i need to give a lengthy essay on how i came to know? anyone know if ill get in trouble with my mentor will become aggravated?