API:Opensearch

Note on case sensitivity
Page name searches are case-sensitive. If $wgCapitalLinks is true (this is the default), the first letter is case-insensitive. If the TitleKey extension is enabled, page name searches are entirely case-insensitive.

Result format
The opensearch API module handles formats differently. It only recognizes XML and JSON (and their * formatted versions); every other valid format parameter results in JSON. The JSON format returns an array containing the search query and an array of result titles.

If the wiki loads the OpenSearchXml extension or is running MediaWiki version 1.25 or greater, which merged this extension into core, then the XML format returns an OpenSearch XML document with titles and URLs. Furthermore
 * if the wiki loads the TextExtracts extension and configures  true, then each Item in the XML format may include a   tag with a text extract from the article.
 * likewise, if the wiki loads the PageImages extension and configures  true, then each Item in the XML format may include an   tag with a thumbnail image from the article.