OptionalformatThe text to be synthesized into speech. If format is TEXT (default), provide plain text. If format is SSML, provide a valid SSML document (for example, <speak>...</speak>).
The name of the voice to use for text-to-speech synthesis. Supported voices include: Emma, Brian, and others. For a complete list of available voices and their characteristics, see the Text-to-Speech Voices documentation.
Format of the message