A typical JSON Path expression is prefixed with $. However, when using JSON Path on Cloud Elements, there is no need to prefix the expression.
By default, JSON Path raises an exception when the field cannot be found. In the example above, an exception would be raised if there was not a city field on the address object. Instead of returning an error, Cloud Elements will return null, which will be removed from the response by default.
JSON Path documentation - https://github.com/json-path/JsonPath
JSON Path evaluator - https://jsonpath.com/