The thing is people in this thread have disagreed on several occasion what is and isn't "implicitly present" in a given description, so that is not an thing that can have an unambiguous answer.
No, but it doesn't need to have an unambiguous answer among the posters in this thread. All that is necessary is for the participants in the game to converge on an answer. One way for that to happen is for the player to do the sort of thing that has been discussed in this thread, and have everyone else at the table (including the GM) go along with it.
it was not obvious to me, that you intended that the players descriptive authority is limited only to what is implicitly present.
I have posted about this several times, and I think you have replied to some of those posts. It's not the only possible way to incorporate players' ideas into framing and setting. But it's probably the most straightforward.
You disagreed with this post in which Lanefan stated that non-DM player doesn't describe the situation.
Here's what I posted in reply to
@Lanefan:
"I punch the nearest dude!" is not describing the situation. It's declaring an action.
That's your interpretation. It's not what the play loop states expressly, and it's not the only tenable implication of what is expressly stated.
The first paragraph is about the difference between describing a situation, and declaring an action. The second is reiterating another point that I've made throughout this thread, that the core play loop does not specify that a player's action declaration cannot refer to something that the GM has not expressly mentioned.
So what's the problem? Certainly it is plausible, that in a tavern a wealthy patron might have accidentally dropped their coin purse?
Your example takes it as a given that
finding a large bag of gold is a meaningful upshot in game-play. That's why you chose a bag of gold rather than, say, a sack of coal.
It therefore raises the question of
under what circumstances is a player's postulation that their PC achieves a meaningful upshot able to come true? Different RPGs answer this question differently. In 4e D&D, as in a number of other RPGs, the approach that I use - (i) because it works, and (ii) because the rulebooks tend to suggest it - is "say 'yes' or roll the dice". In applying that principle, I would also have regard to how many outstanding treasure parcels there are for the current level, which will give an idea of what sort of obstacle/skill challenge (if any) to put between the players and the gold that they desire for their PCs.
If the player (and their PC) gets what they want, then there is indeed a large bag of gold. If the roll/skill challenge (were one called for) failed, then there are obviously a host of candidate narrations possible, none of which require denying that the PC did indeed observe a large sack of
something. Some don't even require denying that the PC observed a large sack of
gold (eg if the upshot of failure is that the wealthy patron who dropped it comes back and thanks the PC for finding it for them).