A couple of the preset options could be pressed into this service:
Questions concerning problems with code you've written must describe the specific problem and include valid code to reproduce it.
Even if code is present, it will no longer be sufficient to reproduce the problem. Another possibility is:
unclear what you're asking
This is a little more far-fetched, but as in Jan Dvorak's example, "what's that Google Reader thing you're talking about?"
If those options are a bit of a stretch, perhaps we can draw on some of the terminology from the Help Center. The on-topic list includes these two items:
- software tools commonly used by programmers
- practical, answerable problems that are unique to the programming profession
To convert those guidelines into a close reason, perhaps variations on the following would work:
...appears to be off-topic because it is not commonly used by programmers
...appears to be off-topic because it does not contain a practical, answerable problem.
And finally, the close reason you posted:
...appears to be off-topic because it is about obsolete API functionality
certainly seems to be usable. It focuses on the what rather than the why, which is probably okay.
It is possible to combine the two approaches at the risk of becoming overly wordy:
...appears to be off-topic because it is about obsolete API functionality which is not commonly used by programmers