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.
Several Months ago, Microsoft announced that the Bing Search API had moved to the Windows Azure Marketplace. This move would make the Bing Search API a paid service with a tiered structure. Developers have been given until August 1st, 2012 to transition to the new version of the Bing Search API.