Create notification from logs

I would like to create a notification when a json file, that gets injected in my logs, gets updated.

We have a service that queries an external service and gets a response in json format. It queries this service every 5 minutes. Most of the time, the json is the same as the previous one, it only changes when it has an update. It is these updates that I would like to catch and trigger a notification.

I only have access to the logs where the json shows.

Would you have any suggestion on how to check that log and if the json has changed, then trigger a notification?