But Bob's player did describe what he was doing. He said he was taking a deep breath and giving it all Bob's got so he could make the jump. I am not sure why that isn't enough, why Bob's player is forced to guess which precise class of actions are considered acceptable when the rules clearly state this is an intended use of an Athletics check. Simply repeating the assertion that the rules demand some particular granularity of description does not make it true.Um, no. in [MENTION=97077]iserith[/MENTION]'s game the player of Bob looks for a boulder strewn along the edge of the chasm and let's Iserith know that he's using the boulder to jump off of to gain some extra distance. Now Iserith makes a decision about the success probability, and if the outcome is in doubt he assigns a DC. Or perhaps he has some other idea he describes. Iserith has said this to you multiple times, so why the misportrayal of his position?
Look at it this way: Bob's player really wants to make this jump so as not to let poor Bob get eaten by a ravening hoard of zombies. She says, "Can I use my Athletics skill proficiency to try and make the jump." In this case, the DM says, "Yes." (because the DM saying yes is almost always better than saying no). If the play fails the roll, the DM says, "Bob steels himself, takes a breath and runs for it. When his fingertips scrape on the opposite ledge before Bob plummets into unending darkness..." Alternatively if Bob succeeds on the roll, the DM says, "As Bob goes to make the jump, he finds a boulder jutting out from this edge of the chasm and using it as a launching point Bob is able to get a couple extra feet and land safely on the other side."
What's the difference? The DM said "Yes" to begin with and let the player use the things on the PC's character sheet to engage the game. Some players will automatically do what you are talking about, coming up with ideas and details all the time. Many will not, however. There is nothing wrong with engaging the game by way of the mechanics, and the DM should recognize and facilitate that player's fun just as much as the DM does with the one writing an epic by way of the table.