From your FAQ, https://jsonapi.org/faq/#is-there-a-json-schema-describing-json-api

I tried to access your json schema at https://jsonapi.org/schema

It gives me a 404.

I am guessing your website should point to this

https://raw.githubusercontent.com/json-api/json-api/refs/heads/gh-pages/_schemas/1.0/schema.json

?