Using the datadog agent typically involves some code added to your service, so you should be able leverage some of the default environment variables (i.e. IS_PULL_REQUEST, RENDER_SERVICE_ID) to determine if data should be sent or not.
Can you provide any details of how you’re pushing data to the agent?
As far as filtering logs sent via log streams to Datadog, we don’t have anything like this available today however, it would be great to capture your particular requirements at feedback.render.com.
Here’s a few existing requests you might just give an upvote on and provide some extra context around your case: