So, for clarity, to use this you need to be a ChatGPT Plus customer (it is built on their technology platform).
I don't require anything to use this custom GPT app, no sign up, no fee etc. and I get no compensation of any kind.
Personally, I use this as a creative tool for inspiration (which is what I recommend, vs. using it to replicate tones). There's plenty of artist tone packs you can buy that will get you way closer to the "real sound" if that's your goal (or if you have magic ears, which I don't). I get stuck in a rut with the same handful of models and barely tap into the hundreds of cabs, amps, pedals, legacy pedals, etc. available, so I like using this to give a creative spark and options of things that generally go together. I also use it as a guitar gear reference and ask it questions about how to use gear, different settings and DSP usage.
Rest assured, if you expect it to give you a perfect signal chain in the right order and tone of the gods, you will be disappointed. The technology isn't that good yet, especially if you ask it to replicate a specific tone from a song. YMMV.