Requirements for Text-To-Speech Engines
[Microsoft Agent is deprecated as of Windows 7, and may be unavailable in subsequent versions of Windows.]
The engine must be fully SAPI 4.0-compliant. In addition, the engine must also support the following SAPI interfaces for tagged text and bookmark notifications. These interfaces enable Microsoft Agent to pace the output of text to a character's word balloon and lip-sync the character's mouth (or equivalent) with the spoken words.