Displaying the URL of the generator when adding doesn't make much sense to me, why not show the generator name?
Adding a generator should also somehow suggest how it can be used by adding something like: "You can use this generator to show a live title of a bookmark by editing the name in the properties dialog of a bookmark this generator applies to" (although this is quite a complex sentence)
Real live example
Does the page Microsummaries contain a real, live, working example? I don't think so. When I bookmark http://finance.yahoo.com/ I do not see microsummaries in the Add Bookmark dialog box. What am I missing?