Only one extremely short letter–EA 223 (EA-el Amarna) is written from Endaruta of Akšapa, and it is a one sentence topic: [following a short 3-sentence formal-formulaic introduction] ... "Whatever the king (i.e. pharaoh), my lord, orders, I shall prepare."
But one perfectly preserved letter from Pharaoh, to Endaruta of Akšapa is known, EA 367. Its topic is to guard (and defend) Akšapa and to prepare for "troop arrivals"-(the archer-forces).
The third and only other reference in the Amarna letters corpus is from letter EA 366 (from Šuwardata of Qiltu (?)), and the letter states:
"...only 'Abdi-Heba and I have been at war with that 'Apiru. Surata, the ruler of Akka, and Endaruta, the ruler of Akšapa, these two also came to my aid, ..."