Microsoft Phone 7 API Documents Already Leaked
One document that was leaked focused on "developer tools", and stated that "Microsoft Visual Studio 2010 and Microsoft Express Blend are the primary tools for developing applications for Windows phones." Another document, called the "partner application development policy", announces that "partner applications will have access to an extended set of managed APIs and a limited set of native APIs. The extended managed APIs are meant to support extending the phone experience with functionality that is specific to a phone or network. This set of APIs supports functionality such as camera mode extensibility."
Developers are waiting for more details with less-than baited breath, noting that the lack of support for C++ makes it more of an entry level API, rather than the upgrade some were hoping for.