Roel van der Hoorn
Hosted Agenda Counter: End the Run is a so called Paid Ability. It means you, as a corp, can hand in the agenda token to end a run.
Another example is Datasucker (Anarch runner card). It says:
Hosted virus counter: Rezzed piece of ice currently being encountered has -1 strength until the end of the encounter.
So you can hand in a virus counter on Datasucker to lower the strength of the ice you're encountering by 1.