This is a paradigm of what Vincent Baker means by "negotiated imagination" - the player's desire for the fiction is I (as my PC) am on top of the wall, the GM's conception of the fiction is You (as your PC) may not make it, given it's a sheer high wall with guards about it. So those two competing conceptions of the fiction need to be resolved an integrated somehow.Picturing discussion
Player 1: I want to get to the top of that wall, quietlyGM: It's sheer and high enough to hurt if you fall, plus as you know there are guards: make a Dexterity (Athletics) check DC 12Player 1: rolls d20... 9+5... 14GM: No problem then, you're at the top looking into the compound...
Avoiding digression into the type of resolution, in order to focus on "discussion" versus "negotiation", I see the agreement here as sustained and implicit. It doesn't feel like what I would call "negotiation."
To ease and constrain the negotiation, the participants use a rule, which can be summarised as having three steps: the GM establishes a target number that the player must roll, and identifies what part of the PC sheet the player can draw on in resolving that roll and then the player makers the roll, draws on the appropriate part of their sheet - ie the bit labelled Dexterity (Athletics) - to modify the roll and then the GM says what happens next.
I don't really care what you and @Crimson Longinus think about the aptness of Baker's use of the word "negotiation", although to me it seems rather apt. The point is that (i) the participants propose their various conceptions of the fiction, and (ii) these have to be reconciled, resolved and integrated, and (iii) one way to do this is simply by talking it out (as might happen in a free roleplaying online game), but (iv) RPGs often use mechanics and the rules around them to ease and constrain the negotiation by establishing certain structures, authorities, etc around who gets to say what when about the shared fiction.
Does anyone disagree with the actual point?