Required JSON: payload.title and payload.description (the full narration script). voice_id is optional; use listVoices to choose a specific voice for the requested locale. Captions default to on, stock videos are the default visual source, and should_export defaults to true. To customize captions, use caption_style for inline settings or brand_kit_config.caption_style_id for a saved brand style.

Generation costs credits and returns a task_id. Poll getTaskResult until SUCCESS or FAILURE. On SUCCESS, read info.export_id (also present in detail.export_id). When should_export=true, poll getVideoExport separately until its status is 3, then read assets.urls[0]. Task SUCCESS means the export was queued; the MP4 may take longer to render.