schema.json

{
	"$schema": "http://json-schema.org/draft-07/schema",

	"definitions": {
		"reference": {
			"type": "string",
			"enum": [ "this will be overridden at build time to contain all style property names" ]
		}
	},

	"type": "object",
	"patternProperties": {
		".*": {
			"$comment": "Recursively declaring all nodes to either be a(nother) nesting level, or a style property",
			"anyOf": [
				{
					"$comment": "a style property with a value",
					"type": "object",
					"properties": {
						"value": {
							"anyOf": [
								{ "$ref": "#/definitions/reference" },
								{
									"$comment": "Not every value is a reference. It can also be a plain string.",
									"type": "string"
								}
							]
						}
					},
					"required": [
						"value"
					]
				},
				{
					"$comment": "a nesting level (`#` refers to the root schema itself)",
					"$ref": "#"
				}
			]
		}
	}
}