Tony's face clearly said 'only one of us plays by the rules', but he was saved from actually saying that out loud and getting himself tried for war crimes by Switzerland. Yeah, sure, exactly that, that's what Tony was trying to do, this was a perfectly reasonable amount of emphatic nodding and pointing. The kid wasn't so into that, though. It gave a knock on Tony's hip to get his attention and have him lean down acceptably enough for the kid to cup a hand over its mouth and honestly, it was a poor facsimile of a whisper, but Tony got what they were going for, "He's going to tickle you." This kid was not under the impression that Captain America could be trusted. That was sensible, Tony like it.
"What's your name again?" he asked.
"Sarah," they not-whispered back, at which Tony balked visibly.
"You're a girl? You know what, we'll deal with that later. Let's hear him out, Sarah. Maybe we can agree to his terms. Is Switzerland prepared to mediate?" When this kid went back to school in the morning, they were going to be prepared to give their whole class a crash course in physics, engineering and international politics. They covered that in (Tony tried to gauge this one's age and grade by height with a flat hand, which did not work at all) elementary school, right?