From their site: This API will allow 3rd parties to programmatically synchronize information, address book, calendar, with the Plaxo network. It is also possible for a 3rd party to develop their own Plaxo client which integrates with a contact management application that Plaxo does not support natively. The API currently supports Plaxo-enabling an address book. Calendar, tasks, and notes are not supported yet, but may be added in the future. The API is currently available as a Representational State Transfer (REST) Web Service.
The following is a list of historical changes that were made to this asset. Typically, once an API is published on ProgrammableWeb.com, the data we keep about that asset gets updated over the course of its life. For example, the endpoint or home page of the documentation might change. As a means of enforcing the integrity of our data, every time a non-trivial change is made to the data we keep about an asset, we require the entry of some changelog text before that change can be saved. This way, we have a great audit trail of all activity surrounding the asset. For each asset, the changelogs begins with the moment an asset is approved for publication on ProgrammableWeb. If you spot an error in our data and believe that a record needs to be updated in some way, the ProgrammableWeb team would very much like to hear from you at firstname.lastname@example.org