In English and many other languages, asking "can you close the window?" is not an inquiry on the ability to close the window but rather a request to do so. Can the (classical) Latin posse be used the same way? I looked at the Lewis & Short entry on posse and found no trace of such use.
I believe that, even if possible, this is not the most idiomatic request. I would rather say fac fenestram claudas or claude fenestram, quaeso. The question is whether a Roman would understand potesne fenestram claudere? as a request and whether there are any such uses is extant literature. Expressing requests as ability questions is a cultural matter, and the Roman culture may have been different from ours in this respect.
