DuckDuckGo !Bang Redirector
The !bang system - in place since 2008 and now spanning thousands of destinations - lets a query like "!w filter bubble" 302-redirect to the destination site's own search (Wikipedia in that example). When called via the Instant Answer API, a bang query returns a Redirect field with the target URL rather than performing the redirect, so it can be used programmatically as a normalized "search-on-other-site" router.