Joseph had integrity (v. 2). The sons of Bilhah were Dan and Naphtali, and the sons of Zilpah were Gad and Asher, and Joseph apparently was their assistant or apprentice, learning how to care for the sheep. Nobody knew it at the time, but Joseph was destined for greater things, and yet he got his start as a servant (Matt. 25:21).
It wasn’t easy for Joseph to work alongside his half brothers because their way of life was different from his. Were the boys robbing their father? Were they getting too involved with the ways of the people of the land? We don’t know what evil things the men were doing, but whatever their sin was, Joseph felt that their father needed to know about it. Joseph also knew what the other brothers were doing and reported that to Jacob.
Did Joseph have the right to inform on his brothers? We’ve always held him in high esteem for his character, but in his youth, was he nothing but a teenage tattletale? He certainly had no authority over his brothers and wasn’t accountable for their behavior, and he was in the fields to work with them, not to spy on them.
Subsequent events proved that, young as he was, Joseph did have common sense and discernment. Thus whatever his brothers were doing must have been terribly wicked or Joseph wouldn’t have mentioned it to his father. Perhaps Jacob suspected that his sons were doing evil things and asked Joseph what he knew. The boy certainly wasn’t going to lie to his father, and when Jacob talked to his sons about their behavior, the men immediately knew who the informer was.