Extend Automation?

my question is about how to extend a 3rd party service. i have an integration that is an ImageProcessingEntity. what i want to do is to be able to pass an arbitrary string into the service when i call image_processing.scan in an automation. this will serve as a context identifier that i’ll then pass along in the payload for an even that is fired. i tried adding something to the data in the service for the automation but that failed because i go the error “extra keys not allowed”. is there an architected way to accomplish this? i have in fact spent time reading the docs and forums but have found nothing.