The Tapir API is really 3: Search, Ping and Post to give you the power to make your blog searchable, get your articles indexed immediately, and push content manually. Indexing of the Rss feed is done at 15 minute intervals. According to the API documentation, the results are returned in JSON or JSONP.
The news of Yahoo's deal to use Microsoft's Bing for search at best has some standing vigil over BOSS and SearchMonkey (our profiles of the BOSS API and Yahoo Search API). At worst, many are already calling the services dead.