His job is to bowl tight overs and he does it well. However, he will only be truly effective when he is partnered with a quality wicket-taking spinner unlike Yasir and Shadab.
His role is to contain, not to attack. Pakistan aren't reaping the benefits of his presence to the full because the other spinner isn't able to take wickets and fulfil the role of an attacking spinner.
Economy is very good and he's currently the best hitter in the side. An important asset in this mediocre Pakistan team.