There is a note on the microformats2 site at the microformats wiki:
Note: use of 'value' within 'tel' should be automatically handled by the support of the value-class-pattern. And for now, the 'type' subproperty of 'tel' is dropped/ignored. If there is demonstrable documented need for additional tel types (e.g. fax), we can introduce new flat properties as needed (e.g. p-gel-fax).
That means that the value-class-pattern is not yet supported by the mf2 spec, but you can try the vendor prefixes and use for example u-x-twitter u-url instead of u-url.
This for example:
<div class="h-card"><a href="http://twitter.com/blabla" class="u-x-twitter u-url">Twitter</a></div>would be interpreted like:
{"items": [ {"type": ["h-card" ],"properties": {"x-twitter": ["http:\/\/twitter.com\/blabla" ],"url": ["http:\/\/twitter.com\/blabla" ],"name": ["Twitter" ] } } ],"rels": {}}BTW: You can try/validate your code here: http://pin13.net
