This may have been covered already in some prior posts on the site, but I’ve found myself typing something like it in an email again, so I thought I’d put this out there in a post of its own:
That’s the “secret” of assessment, declaration, and maneuvering, in fact — they’re all the same action, in essence, a skill roll that gives rise to an aspect, which offers a free invocation (tag) out of respect to the successfully skill roll. The only difference between them is in terms of how the authority model appears to work.
Assessment is a discovery of something the GM thought of, uncovered by a successful skill roll. Because the aspect is presumed to exist prior to its discovery, you can look at the possibility of “getting it wrong”, as we do with some of the Empathy/Deceit interactions in SOTC and DFRPG, but that’s not a necessary feature.
Declaration is the establishment of a player-invented/introduced fact, backed by a successful skill roll. The fact is presumed to exist prior to its introduction, as far as the characters are concerned. The player’s character, typically, is the smart/alert one who’s on the ball enough to take advantage of the fact first.
A maneuver is a character-imposed change in circumstance, successfully established if the player makes a (often contested) skill roll on his behalf.
But outside of those authority models, it’s the same basic game move.