{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "type": "object",
    "properties": {
        "foo": {
            "readOnly": true,
            "type": "string",
            "example": "123"
        },
        "bar": {
            "type": ["string", "null"],
            "format": "uuid",
            "example": "12345"
        },
        "baz": {
            "type": ["string", "null"],
            "format": "date-time"
        }
    },
    "required": [
        "foo",
        "bar"
    ]
}