pemerton said:
If the GM calls for a check and the check succeeds, then the player's intent is realised
No, I didn't miss that you have complete discretion on HOW that intent is realized. You can pick any way you choose that meets his intent, and there will usually be many ways.
You are just making this up.
From BW Gold (pp 24-25, 30):
Let’s start with the core of the Burning Wheel system. We call it “Intent and Task.” . . .
What do you want do and why do you want your character to do it? . . .
When a player states “I kill him!” we know his intent. By describing how his character will undertake this intent, he defines the task. Clearly stating and linking the task and intent allows player and GM to determine what ability needs to be tested. . . .
A task is a measurable, finite and quantifiable act performed by a character: attacking someone with a sword, studying a scroll or resting in an abbey. A task describes how you accomplish your intent. . . .
[W]hat happens after the dice have come to rest and the successes are counted? If the successes equal or exceed the obstacle, the character has succeeded in his goal - he achieved his intent and completed the task. . . .
A successful roll is sacrosanct in Burning Wheel and neither GM nor other players can change the fact that the act was successful. The GM may only embellish or reinforce a successful ability test.
In other words, it is the
player who establishes what happens in the fiction as the reasult of a successful check.
From the MHRP rulebook (pp OM46, OM50):
As a player, when it’s time for your action, you need to make your intent as clear as possible to the Watcher and other players before you even pick up the dice. If you’ve said what you want to do, make sure you’re suggesting what you want out of the action. . . . Knowing what you want if you succeed and what you think will happen if you don’t is key to the next step. . . .
Once you have the two totals (action and reaction) you can compare them to each other. You’re looking to see if your opponent’s reaction total is greater than your action total. If this is the case, your action fails. . . .
If the reaction total is equal to or lower than your action total, your action succeeds. You can use your effect die to create an effect: stress, an asset, or a complication.
Again, it is the
player who establishes the consequences (in the ficiton, and their mechanical expression) if a check is successful.
From the DitV rulebook (p 54):
To launch a conflict, we begin by establishing what’s at stake, setting the stage, and figuring out who’s participating. Every participating player [which may include the GM if its not PC vs PC] takes up dice to match the circumstances and throws them down all at once. From there on, the conflict plays out kind of like the betting in poker. One player “raises” by having a character act and putting forward two dice to back it up, and all of the other players whose characters are affected by the act have to put forward dice of their own to “see.” When you use dice to Raise and See they’re gone: put them back in the bowl and don’t use them again in this conflict. . . .
Anyone who has too few dice to See when they have to — and can’t or won’t escalate — is out of the conflict. Whoever’s left at the end gets to decide the fate of what’s at stake.
If the player of a PC wins the conflict, that player gets to decide the fate of what's at stake. The GM has no discretion here.
As I said, your assertion that the GM has discretion to narrate the outcome of a success is just made up. That may be true in some RPGs (eg I'm sure that the 2nd ed AD&D rulebooks say something like this). It may be accepted at some tables. It is not consistent with "say 'yes' or roll the dice".