Beta Two of Windows Live Writer introduces a set of APIs which can be used by weblog providers to customize both the capabilities of Writer as well as add new capabilities to the Writer user-interface. Available customizations include:

• Defining the subset of weblog features supported by the weblog. This allows providers to implement any subset of the core XML-RPC based weblog APIs (Metaweblog, Movable Type, or Wordpress) and have Writer’s UI correctly respect this subset.
  
• Provide the correct URL entry points for viewing and managing the weblog as well as editing posts online.
  
• Define a custom icon and watermark image that appears in the Writer Sidebar
  
• Define custom buttons that can link to web-pages, display content in a drop-down, and notify the users of new content and other online activity.
  
• Define WYSIWYG editing templates for the active weblog theme.
  

This document describes these customization capabilities in detail.