Credibility is compromised of people who are unreliable narrators. Sometimes these narrators make theur writings in the first person, although they also do it in the second and third person. These narrators have some classifications, they are rogues, crazy, clowns, naive and liars.
The correct option is: Authoritative, because the word means that it´s energetic and tenacious in it´s history which agrees with the characteristics of these unreliable narrators.