Agents are of two kinds, super agents like Kia or Raiola or family members. In the former case the agents themselves have extensive scouting networks and are aware of the talent pipeline even before the European clubs, and in the latter case its like the player gets some more money for himself, as his family is just an extension of himself. In both cases there are pros and cons. In case of super agents, you'll know that the player will be always unstable, but they'll definitely be easier to shift if things don't work out, a la Mkhitaryan. In case of family members you've got cases like the Aouar one where the agent wants too much for himself even at the cost of Aouar's career. Ideally he should've played at a club like Arsenal for 4-5 years and then gone on to Real, Barca, Bayern if he wanted to. A super agent would've got that deal done, because they know that there's more money to be made down the lie and they don't have to kill the golden egg laying hen right now.