Custom Toon shader for Substance Painter

Hi. I had been googling for some hours now, and I cannot find a reliable source to read about the API to create a toon shader for substance painter 2019. Why? I am asking Chat GPT and Claude to walk me through the basics of writing gsls code, and I'd like to do a simple ramp for a toon shader.
I've done the toon_shader.sbsprs, toon_shader_frag.glsl, toon_shader_vert.glsl, toon_shader_icon.png, but I get errors for compilation and when I select the new shader, my mesh becomes pink.

Please help me find the documentation for this. Thank you.