I usually find myself constantly linking to methods and properties in publically available docs for frameworks or libraries. I'd like to suggest an autocomplete feature when you enter a link in a special format to embed the link automatically to a relevant API doc.
Question tags can be used to help the autocomplete filter the results to keep them relevant.
Usecase Example 1: Linking to Java API doc on a Java tagged question
I'm answering a question on a java tagged question. So when I enter
api:toString the editor should open up a context list and give suggestions such as
Usecase Example 2: Referring to another API doc on a Java tagged question
I'm answering a question that is a java framework, .e.g. play. So when I enter
api::play:Play.version it will give a suggestion to
Play.version. The double colon is there to indicate that you are referring to another API doc (so it doesn't collide with the ones in the question's tags).
This could also be extended to suggest frameworks that are tied to a technology. E.g. in a question with the Java tag, typing in
api::p would suggest frameworks that begin with the letter P that are tied to Java such as Play Framework, powermock, etc.
Obviously this will require scraping api docs, but they are most of the time formatted in the same way. Also there is the issue to select what API docs to support, but this could be limited at first. I'd think focus should be on .NET and Java or whatever is the popular technology or framework on stack exchange.
I think this would be a nice to have feature on stackoverflow (and other programming related stackexchange sites such as programmers and game development). But I can imagine that you don't need to just have links to api docs. On sites such as superuser, ubuntu or unix something such as
man: would autosuggest inserting link to a man page.