Looking for the length of the hint list seems a fragile. Maybe there could be multiple function signatures. Maybe some other single item would wrap that shouldn't.

Another idea would be for the provider to add a flag to the hintsObj which is passed into this method. In the JavaScriptCodeHints provider, this is the hintResponse that's created in the getHints() method and passed to $deferredHints.resolveWith() callback. What do you think of that idea?