There are a ton of issues with that.
That doesn’t automatically mean it’s the wrong move, just that it’s fraught with problems.
Ultimately, most people feel that roleplaying works best when everyone, ya know, plays a role. As in, behaves as their character would, based on what their character knows, rather than how they would, based on what they know. This is usually the goal.
However, most groups don’t explicitly enforce it. It’s considered bad taste to meta-game, it’s considered good roleplaying to stay in character even when it hurts, but there aren’t specific rules about it, and in many groups the DM claiming “your character wouldn’t do that” is a gross violation of the player’s area of control (i.e. their character). Statements to that effect have been reasons to leave a group for a lot of players in a lot of situations, and while I am lucky to have never played under a DM who seriously thought that was his business, if I were I most likely wouldn’t tolerate it.
But your group may be different. You are expressing frustration with the status quo, and that is presumably a feeling shared by others. This could be a solution to that, and ideally the questioning would come more as a reminder than as any real attempt to control others’ characters.
That said, the objections of some people in your group suggests that not everyone feels the way you do. There are people in the group who either A. feel they are not metagaming, or B. feel that the metagaming is a good thing, and in both cases there is not a problem. Both perspectives are valid, though B is a bit unusual. (There is a third option, C, wherein people recognize that there is a problem but dislike this solution; I would probably fall in that category. That said, these people are probably already doing their best not to metagame.)
So what you really need to do is discuss metagaming, what is or isn’t and how much is or isn’t appropriate. You need to have a mature discussion, and you need to listen to others’ opinions, perspectives, and preferences. More than likely, no two people in the group will exactly align, but hopefully everyone will be near enough to some common ground that a compromise can be made.
And once you have that, you really probably don’t need this rule. You might include it, in theory, if people felt they needed to be reminded or “called on” for metagaming, but I really cannot imagine any point where it is a good idea for a DM to say “no, your character would not do that.” You can question an action (though even that might be disrespectful), but ultimately the DM has to back down there because his authority, so absolute otherwise, cannot control player characters like that, or else the players have nothing and there is no game.
Under no circumstances should this rule be even considered unless everyone wants it. A group that agreed it would be for the best to get called in this fashion could work. But if some do, and some don’t, it is not a reasonable thing for a DM to expect of players. The individuals who requested it could get called on it, but you should never tell someone he’s not playing his character right, after he’s specifically told you to stay hands-off on that subject. Were it me, I would walk out the very first time it happened, assuming you convinced me to stay at all, which I tend to doubt.
There can still be a compromise even if people object to this as a rule, of course; that’s actually normal for most groups. E.g. if you say something like “I won’t call you on it, but it is your responsibility to avoid metagaming and this game isn’t going to survive if you don’t.” and he says “OK, I will do what I can,” that is a workable situation.
But if no compromise can be made, if some feel that their behavior is entirely appropriate and refuse to modify it, and you feel your expectations are entirely reasonable and refuse to modify those, then you have learned this without going through it the hard way: you are not a compatible group of people who are looking for the same game. That’s pretty much what you’d discover if you tried to “enforce” these rules without a compromise, but there’d be a lot more ill feelings. Better to skip that step.
Normally I don't answer questions after the answered sign has been given, but I do believe that there is still much to say. So without much farther ado, let's dive in.
Yeah, it has been written before, but it still worth mentioning. If your players didn't give you a clear description, ask them for more input. While some of the answerers did suggest that you should not ask leading questions, many a time you actually should. From my experience, many of the shortest descriptions for actions come from players who didn't get the full picture in the first place. As such, leading them a little bit (or even more than a little bit) will help them to see the picture more fully for their next descriptions.
Furthermore, you stated that your players are new. New players don't always know what is expected from them and what is not. By leading them a little bit with your questions you actually help them to better grasp what should be described and what not, and to what extent.
Lead from example
You are their GM. They look at you, with their big eyes like you're some kind of a teacher figure and they try to understand from what you do what they should do. This means one simple thing: If you'll describe your actions, they will describe their actions. They will probably start slowly, but sooner or later it will come. Let them see in your descriptions what is expected from them.
Reward for great descriptions
You're using FATE, so use your fate points for your advantage. fate points are supposed to move all the time, to be given and spent very very quickly. This thing enables you to give extra ones without fearing for your adventure/story. One of the players gave a great description? Give her a fate point while explaining for what this is given. "See what Lisa did there? Describe your actions like that and the next Chip is yours…"
The spending mechanics are geared toward describing too. In order to spend a fate point you have to either describe or to be in a situation where one of the aspects comes into play. Build on that, make them add those nifty extra details in order to use those fate points of them. Remind them that by describing they'll be able to unlock those special abilities and possibilities.
Make them swim in details
Although you shouldn't take this literally, do your best to build a picture in their heads of what's happening. As I've mentioned before, many short descriptions from the players come from not understanding and not seeing the big picture of the scene. When they don't know that there's a barrel in the left they won't use it. Make them see the barrel and they'll use it. You're their senses, so what you don't describe doesn't exist.
Let them add small details
The last paragraph is true with one exception: If your players suggest adding a small detail here or there, let them. Sometimes they'll need to spend a fate point, but only when it really is important. If, for example, they're in a combat and one of them asks if there's a barrel at the end of the market, ask yourself if it is logical to find one in there. If so, give it to them. Many a time, with these questions they try to ask you if their idea is good. If you'll give it to them many a time they will come with one of those legendary acts. As a rule of thumb, if it is useful to this particular scene only say yes.
A Style or Category More Than a Tool
There is a style of games in which the GM gets to be surprised and explore unknowns. These are games where the players also have the right to add story details, places and NPCs to the game world, and otherwise take over parts of the usual GM's repertoire of powers.
In some games, such power is highly restricted and/or regulated. In others, the line between the GM's and the players' ability to directly shape the world by fiat is much blurrier.
These games are known by a plethora of names such as 'collaborative', 'narrative', 'storygames' and perhaps some others. There is surprisingly much flame-warring about what exactly 'narrative' means what are minimum requirements for a game to use such adjectives. But that's not as important to this question as understanding what games should help with your problem: games where the GM gets to explore parts of the world created by players in a manner similar to how players explore the parts made by the GM.
Examples of such games:
The Cost of Discovery
Of course, such a style is not necessarily for everyone, and not just in terms of being not to everyone's taste. GMing in such a style requires being more ready and willing to improvise, to tolerate carefully set up plans being invalidated by a seemingly-inconsequential detail that turns out to significantly change the context and the like. It can result in the game world ending up less coherent under the weight of all the additions - more Star Wars Expanded Universe than Historical WWII. If you and your players are fine with that - great!