Cap'n Kobold
Hero
Outside of phrasing and syntax pedantry, filling in things that the character may know but the player does not is part of the DM's job. Whether that is what the weather outside the inn is like, to the name of the mayor of the town that the character lives in. If I think that there is a reasonable chance of the character knowing, but it isn't definite, I may call for a roll and then give information to the player about what their character knows.I disagree with your first sentence, though. The DM's job is to describe the environment and the results of the PCs' actions. What a PC knows is not part of the environment. If a player wants to establish that their character knows some piece of information, s/he's free to do so by deciding that's the case. If s/he wants to verify that the information is correct, however, then s/he needs to take some sort of action to do so, which can then be adjudicated. Then we're playing D&D, not 20 questions.
I don't make a player climb up the side of the house for their character to successfully scale a cliff. I don't make a player read the Monster Manual in order for their character to know where the closest place to find bulettes is.