The robot had artificial intelligence programming for decision-making and autonomous activity. It complied to direct orders and was capable of maintaining ship systems and operating controls such as those on a transporter. It had a vocal interface.
It was 3-4 feet tall, metallic, with three main sections. The spherical upper section contained a sensor array that lit up green, yellow or red depending on its alert status. A host of mechanical implements such as grappling arms were joined to the body at the base of the upper section. Its base was wide and allowed the robot to slide along the floor. It made whirring sounds when it moved. Interior components were accessible from at least one hatch in the midsection. (TOS comic: "All the Ages Frozen")