Normally, players have the option of spending 1 XP to reject a GM-intrusion. How much information do the players have about the intrusion when deciding whether to accept or not? More specifically, do they know the difficulty of the intrusion?
When I offer an intrusion, I have been doing something like this:
GM: As you begin digging through the rubble, it caves in on you! This is a GM-intrusion. You can reject it by spending 1 xp, or you can accept the difficulty 3 task and get some xp.
However, I am considering whether or not I should disclose the difficulty upfront, or keep it secret.