BSDF to RGB

[kit2cuz]

I often make a cell-style toon rendering for Eeeve in Blender.
In Eeeve, I can customize a variety of toon shading graphs in combination with Shader to RGB and Ramp nodes.
While in Cycles, there is only Toon BSDF which is not easy to customize as I expect.
I know there are no APIs to convert BSDF to RGB in OSL.

I hope OSL to prepare such APIs to convert BSDF to RGB.