The Invisible Blade's Unfettered Defense feature (CW 46) says:
An invisible blade benefits from an increased survival instinct during combat. Because of this sixth sense, he adds 1 point of Intelligence bonus (if any) per invisible blade class level to his Armor Class in addition to any other modifiers he would normally receive. If the invisible blade is caught flat-footed or is otherwise denied his Dexterity modifier to Armor Class, he also loses this bonus. Unfettered defense functions only when an invisible blade is not wearing armor and is armed with one or more daggers, kukris, or punching daggers as his only weapons.
For the purposes of benefiting from Unfettered Defense, are you considered wearing an armor when under Mage Armor spell?