Here are their bonuses excluding traits, and typical manipulate , assassinate, demoralize stuff:
I'll break it down. All % or +/- will be at rank 3 (highest rank).
Deployed in your territory
- Cultural Conversion +9 / +18 (2 different skills one in the authority tree, the other in zeal. This also works in enemy territories)
- +15% tax rate to local province (When Deployed)
In your army
- -18 % Upkeep Cost on Military
- +18 % Movement Range
- They also give you a little defense versus enemy agents
Deployed in the enemy territory
- -15 % Tax Rate
- + 90% public order penalty due to local presence of foreign authority
- - 30% Wealth from all commerce buildings
My most common use is to deploy them in my highest grossing provinces for the extra tax. They usually end up with traits that will give bonuses to public order. After that, I usually go for evading enemy agents, and assassination since it's built into the "Politics" talent.