Custom Rules allow you to validate your analytics and marketing tags against expected values. You can set up rules to test tags, variables, and values to confirm each matches a specific RegEx pattern (like a campaign code format). If a rule fails to meet its criteria, the failure will show up in your Reports or you can set up alerts to notify you immediately.
Using rule filters, you can make rules fire based on URL, status code, or tag type. With conditions, you set the parameters to validate against the tags or pages that correspond to your filters. By combining filters and conditions, you can test your tags with a high level of detail.