ActionHelpers.MousePick takes a float pick distance and an int layermask. It returns a RaycastHit, trying to use cached values compatible with the pick distance and layermask. This allows many actions to use MousePick without each one doing it's own Raycast (which can get expensive).
Be aware that ActionHelpers aren't documented right now and are subject to change. You can use standard Unity Raycast methods instead to be safe...