An agent, or spy, is an individual who follows orders from the player. You can assign them to missions as you see fit.
Through study and actions, they develop skills such as sword fighting or persuasion over the course of their careers to better fulfill your objectives.
Due to the timeline of the game it's entirely possible you could recruit an Agent at the age of 18, work them, then retire them at 70 to teach your newer agents. That's assuming they survive anyway, since they won't maintain their physical fitness as they age anyway.
Through study and actions, they develop skills such as sword fighting or persuasion over the course of their careers to better fulfill your objectives.
Due to the timeline of the game it's entirely possible you could recruit an Agent at the age of 18, work them, then retire them at 70 to teach your newer agents. That's assuming they survive anyway, since they won't maintain their physical fitness as they age anyway.