Currently, PropertyDescriptors can be configured with a Validator that validates any proposed value. Rather than solely driving what's allowable through the Validator which only exists at runtime, it may be beneficial if the PropertyDescriptor can describe the type of input they support. For instance a file, a list of files, a URL, etc.
Using these details to populate the extension metadata generated at build time would be helpful in use cases where the flow might be authored separate from the runtime environment like Stateless NiFi.
Having these details may even provide an opportunity to update the Processor API to support default file exists validators, URL validators, etc. Also, it may allow for the Processor API to offer capabilities around loading the content from these configured value.