schema.json

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "properties": {
        "FieldWithAnonType": {
            "properties": {
                "SubfieldA": {
                    "type": "number"
                },
                "SubfieldB": {
                    "type": [
                        "string",
                        "number"
                    ]
                },
                "SubfieldC": {
                    "properties": {
                        "SubsubfieldA": {
                            "items": {
                                "type": "number"
                            },
                            "type": "array"
                        }
                    },
                    "required": [
                        "SubsubfieldA"
                    ],
                    "type": "object"
                }
            },
            "required": [
                "SubfieldA",
                "SubfieldB",
                "SubfieldC"
            ],
            "type": "object"
        }
    },
    "required": [
        "FieldWithAnonType"
    ],
    "type": "object"
}