Yahoo! Address Book API now open to 3rd party developers

One of the most valuable features of any good email or IM service is the contact list. Yahoo!, Google, Microsoft, and other companies that provide online communication tools also give you a place to store information about your friends, family, colleagues, and people who you met years ago and have completely forgotten about.

Yahoo! is making that much more useful by launching the Yahoo! Address Book API, which will let 3rd party developers create applications that can interact with your contact list. For example, you can use the API to develop an application that will scan your contact list to find other users who already belong to the social network you're signing up for, or a list of people you may want to invite. The API also supports contact synchronization, which could come in handy if you want to develop a tool that syncs online contact lists with Outlook or Thunderbird.

The API also provides the ability to create, modify, or delete contact information, which sounds a litle scary. But Yahoo! says write-acess is "available on a case by case basis," so developers will need to contact Yahoo! before creating a utility that has the ability to wipe out your address book.

Plaxo and LinkedIn have been using the API for a while, but Yahoo! is launching it publicly today.