Citoid is an extension that allows you to add citations from a url or other identifier from the Visual Editor.
Install mediawiki, enable citoid, and make sure to import the listed templates:
We should show the "we could not make a citation for you" error if no template parameters have been added to the citation. We could check to see if the template is empty of parameters before offering up the suggestion in the inspector. You can mimic this behaviour locally by removing the template data ( i.e. content between <templatedata> tags in Template/Cite_web/doc) and then inserting a citation in visual editor from a url that would be a web citation i.e. http://twitter.com.