If you want a toon shader, then the solution is a lot simpler. Create a 2 color output and choose your colors. The second colour will be the outline.  Plug this to a "angle of incidence" node ( not an incident light angle node). Insert a filter between nodes. The shape of the filter will define how thick the outline will be. The filter should only use straight lines ( not smooth curves), otherwise, there will be some blending between the 2 colours.