I'm not sure what tag is set in the API call, and trying to get a packet capture of that might be an adventure...
BUT, you can set it from the Secure Malware Analytics/ThreatGrid (TG) side.
You are entitled to a "Device Management" account, that lets you see what's getting send to TG from your devices. Check with your Cybersecurity Sales person.
Once you have that, open a TG TAC case and have your ESAs/WSAs/SMAs (CES included!) added to that account... they'll want your TG Organization name and your login id, and the "File Analysis Client ID" from your appliances.
They show up as users in the TG console, and you can set how their files are treated, public vs. private.