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.

Example
The opensearch API module handles formats differently. Only XML and JSON (and their formatted versions) are recognized, every other valid format parameter results in JSON. The JSON format returns an array containing the search query and an array of result titles:

Furthermore, the XML format returns an OpenSearch XML file with titles, URLs and short descriptions when OpenSearchXml extension is loaded: