We use a first reply SLA that works well. However, some tickets simply do not require agent interaction, and can be resolved immediately. We would like an automatic method to exclude those tickets from the SLA, primarily because now they generate agent notifications when the SLA warning/fail states trigger.

To be clear: it is easy enough to exclude these tickets from reports on the SLA, so that's no issue. One could also manually remove the SLA from such tickets, but this is a lot of hassle. There also seems to be no way to write a trigger that checks if the ticket has > 0 agent messages, which could be used to remove the SLA from a ticket once it is resolved without agent messages in it.