When the black suit, sunglasses, jet pack, laser rifle, or circling Avengers Quinjet doesn't get the point across.
There's a massive Super-Adaptoid leveling New Jersey and you need to get through the police perimeter to support Captain America, Nick Fury, Vision, and the Scarlet Witch.
Sure, you look the part, but the local Sheriff isn't buying it. You need something official -- something signifying your unquestionable employment with the world's premier super-spy organization.