opensearch

https://developer.mozilla.org/en/Creating_OpenSearch_plugins_for_Firefox
OpenSearch description file

<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/"
                       xmlns:moz="http://www.mozilla.org/2006/browser/search/">
<ShortName>engineName</ShortName>
<Description>engineDescription</Description>
<InputEncoding>inputEncoding</InputEncoding>
<Image width="16" height="16" type="image/x-icon">data:image/x-icon;base64,imageData</Image>
<Url type="text/html" method="method" template="searchURL">
  <Param name="paramName1" value="paramValue1"/>
  ...
  <Param name="paramNameN" value="paramValueN"/>
</Url>
<Url type="application/x-suggestions+json" template="suggestionURL"/>
<moz:SearchForm>searchFormURL</moz:SearchForm>
</OpenSearchDescription>

Autodiscovery of search plugins

<link rel="search" type="application/opensearchdescription+xml" title="MySite: By Author" href="http://www.mysite.com/mysiteauthor.xml">
<link rel="search" type="application/opensearchdescription+xml" title="MySite: By Title" href="http://www.mysite.com/mysitetitle.xml">