The clamp meta is only useful for property editors when designing / configuring from the editor panel. That meta does not even exist without the editor. They can not be used for proper validation and will not automatically clamp a value when you set a property from code. The easiest way to set up value validation is to make your properties private and validate through public setter methods. In the case of functions just validate the arguments within the function and print a warning when something is not what you expect, or clamp a value if that is what you wish, or assert if an input may never be a wrong value.