he normal behaviour for the update centre json was to take the content the excerpt macro on the wiki page in order to fill in the description in the update centre.
This sometimes fails when the url in the pom does not match a jenkins wiki url, hence leaving the description (and link) empty in the update centre

I know Alan Harder did some magic behind the scenes so it worked with my two plug-ins, but I think it should be made consistent so that it always takes URL and description from the pom file and not rely on the wiki.