Social bookmarking site del.icio.us has exposed a new API providing the top tags and total number of bookmarks for any URL in its system. Yahoo’s Developer Network provided a short preview earlier tonight of a soon to be released del.icio.us web badge but currently anyone can request data from the open API . It’s a useful feature to provide additional context for a URL , suggest tags, or measure one aspect of a site’s popularity.

endpoint http://badges.del.icio.us/feeds/json/url/blogbadge parameter hash

Simply submit a request to the above API endpoint with a hex MD5 hash of the URL of interest as your hash parameter value. Del.icio.us returns results in JSON key-value pairs. Data includes the total number of del.icio.us users who have tagged the given URL and the top 11 tags (and tag count) used to describe its content.

You can check out a few examples such as the response for del.icio.us, the response for apple.com, or the response for niallkennedy.com/blog. If you need help constructing a MD5 hash you can use Paul Johnson’s implementation (del.icio.us uses the same script). You may specify a callback function using the callback parameter.

The API is officially unreleased, may be shut down if not used in full Yahoo-constructed blog sidebar badge form, and may be subject to further terms of service. Hopefully the new set of del.icio.us servers can keep up with demand.