Last modified: 2011-03-13 18:05:01 UTC
Please add "disambig" flag to prop=info. It's very simple, just check, if this page transcludes MediaWiki:Disambiguationspage.
The query would be fairly simple to implement - just query the links from [[MediaWiki:Disambiguationspage]], and check if any of the transclusions in the given titles are in that list of links.
The question is: Should the disambiguations be exposed on the API level? The client may just as well query links from the [[MediaWiki:Disambiguationspage]], and later check against the list of templates for the given pages (which is usually very short). The bandwidth cost is small, but this way the API is not hardcoded to the concepts of page disambiguations and the api is faster because the client may cache the list of templates whereas server will not and would have to query [[MediaWiki:Disambiguationspage]] list every time.
I will WONTFIX this for now, unless there are some good arguments for it.