Xenophon's Cyropaedia: Cyrus limits the carrier to the letter's content, not expanding authority

In Xenophon's Cyropaedia, Cyrus gives a letter to a carrier and instructs him to answer questions 'in accordance with' the letter. Mike argues this is a special command in one situation, not evidence of a general custom. Moreover, it limits the carrier to what's written rather than expanding his authority to interpret or teach. The injunction to answer 'only in accordance with what is written' restricts rather than empowers.