The API documentation is divided into four sections:
Getting Started with the MetaWeblog API for Windows Live Spaces contains information about setting up your blog for remote editing.
About the MetaWeblogAPI and Windows Live Spaces contains information about the Service Endpoint, authentication procedures, and the date and time format used by the API.
The MetaWeblog API Reference contains reference materials for the methods supported by the MetaWeblog API.
MetaWeblog API Code Samples contains samples written in C# and Visual Basic.