We describe key affordances required by tools for developing haptic behaviors. Haptic icon design involves the envisioning, expression and iterative modification of haptic behavior representations. These behaviors are then rendered on a haptic device. For example, a sinusoidal force vs. position representation rendered on a haptic knob would produce the feeling of detents. Our contribution is twofold. We introduce a custom haptic icon prototyper that includes novel interaction features, and we then use the lessons learnt from its development plus our experiences with a variety of haptic devices to present and argue high-level design choices for such prototyping tools in general.