On http://search.musicbrainz.org/ws/2/url/?query=url:%22http://www.samihyde.com/%22 that was linked in IRC, we have:

<target id="52b3cad0-9622-4b39-ab22-9a0d44c7b86f"/>

The target@id attribute was only added to deal with relationships to URLs (which, as we don't have any URL-URL relationships doesn't apply to this endpoint), where for historical reasons (i.e.: I don't really know why, since the decision predates my involvement, but we can't break compatibility without a very good reason) the target pointed to the url (i.e. <target>http://www.samihyde.com</target> as you can see on http://musicbrainz.org/ws/2/artist/52b3cad0-9622-4b39-ab22-9a0d44c7b86f?inc=url-rels ). To include the URL MBID, therefore, the @id attribute was added so that the final result – for URL relationships, and only them – is <target id="044dc214-8bee-435a-88d3-a125df5918d6">http://www.samihyde.com/</target>

To be compatible with lookups, /ws/2/url search should be returning:

<target>52b3cad0-9622-4b39-ab22-9a0d44c7b86f</target>

If you'd prefer to have <target id="52b3...">52b3...</target> that would also be fine, though I imagine you can see that this would look a bit silly.