When you delve into the world of Jäger you are stepping into the territory of the second most versatile character in the game.
His mobility as well as his well rounded Carbine make him a great roamer. These together mean you can counter a pincer as you can easily push one, secure the kill and then make your next move from there. You can roam actively getting long range picks with the Acog then running away to go on a long flank for another pick, or roam passively and use map knowledge and speed to waste attackers time.
Alternatively, you can very effectively camp obj, since his reliable carbine + Acog means he can safely hold down angles that other defenders couldn't. Although many considered this a wasted use of Jäger as a Rock, Doc or Echo could do this allowing Jäger to roam (but sometimes it's useful to know that Jäger can fulfil this role if mid-round the previous op there dies).
Alternatively (again), Jäger can hold an important room above or next to the objective, using his ADS to prevent the attackers from fragging or flashing him out. Paired with a Mute who can prevent drones, you can completely deny attacker access to a certain hatch or wall while maintaining the threat of a flank whenever it's needed.
On certain maps or sites where attackers are constantly repelling, Jäger is ideal for doing run outs as he can run out, kill the attacker and run back in faster and more reliably than most other ops.