Any code logging an event must declare a schema for it, see m:Special:PrefixIndex/Schema: for a list.
Several extensions are logging client-side events using this extension's
Register the version of schema you are logging againstEdit
This is done here in the MobileFrontend https://github.com/wikimedia/mediawiki-extensions-MobileFrontend/blob/master/includes/MobileFrontend.hooks.php#L865
Other schemas appear here:
Several extensions log events on the server using
EventLogging::LogEvent(): Campaigns, CentralAuth, MobileFrontend, WikimediaEvents, etc .