I've read a few fan theories my favourite being that he's actually Roller, Orion Pax's mysterious partner from before the war, and that he's undercover as Tarn, the leader of the DJD.
The fact that they both share a similar body build and some design elements supports this theory. There is also Vos.
However, we know Agent 113 drops his inside information via special non-lethal bullets he shoots into the left eye of an Autobot insignia of his "victims".
That requires a firearm, so far the only DJD members to be seen with a firearm are Tarn and Vos. However, Tarns firearms are more on the "everything goes boom" side, while Vos turns into a sniper rifle.
Vos also has the cover of "not speaking" modern-day Cybertronian, which will make him odd to the rest of the DJD and thus, easier to get away with not knowing things, since you know, he doesn't understand.
So I think Tarn is a red herring, while Vos is the actual Agent 113, but I believe Tarn really is Roller, after having switched sides fully convinced of the Decepticon way.
Just something that I've been thinking about, any input?