Shit, my bad, hah.
It's Agility for stealth-related actions.
So, Average Schlep for agility. You can't fail due to your Agility of 4, however go ahead and roll and see how many extra descriptions you get, then post your roll and your action with descriptions, if any.
Note: You do not have to use all of your decsriptions. You may also voluntarily fail, even if you rolled and succeeded, if you wish. Sometimes it can be more advantageous.