Does https://json-schema.org/ not work for you?
The thing about XML Schema, is that it is completely "baked into" pretty much every tool and library out there, so you can do "on-the-fly" runtime validation.
JSON is really about minimizing text. It works really well for this.
Another issue, is that JSON doesn't have comments, so it can be difficult to annotate a JSON file.
{
"$schema": "http://json-schema.org/draft-07/schema#",
"type": "object",
"properties": {
"price": {
"type": "number",
"multipleOf": 0.01,
"minimum": 0
},
"currency": {
"type": "string",
"enum": ["EUR", "USD", "GBP"],
"default": "EUR"
}
}
}