List Synthesia avatars available for video creation: stock avatars from a bundled catalog snapshot, plus any custom/personal avatars registered in the local server config. Returns avatar IDs to use as the avatar field in create_video. Note: Synthesia has no API endpoint for avatar discovery, so the stock list is a snapshot and may be incomplete; custom avatar IDs must be registered in the config file (copied from STUDIO via the avatar's three-dot menu → Copy ID).

List Synthesia text-to-speech voices: stock voices from a bundled catalog snapshot plus custom voices registered in the local server config. Returns voice IDs for the avatarSettings.voice field in create_video. IMPORTANT: voices are optional — if omitted, Synthesia automatically uses its recommended voice for the chosen avatar, which is a good default. The stock list is a snapshot and may be incomplete.

List Synthesia video templates (created in STUDIO) with their IDs and variable names. Templates are the way to produce rich, designed videos via the API — use create_video_from_template with a templateId from this list. Paginated: pass the returned nextOffset as offset to fetch more.

Retrieve a single Synthesia template by ID, including its full variable list. Call this before create_video_from_template to see exactly which templateData keys are expected (variable names are case-sensitive).

Create a Synthesia avatar video from one or more scenes (avatar + background + script each). Rendering is asynchronous: this returns a videoId immediately; check progress later with get_video. DEFAULTS TO A FREE DRAFT (watermarked test render); pass render_mode='final' only when the user explicitly wants to spend quota on a final render. For visually rich layouts (on-screen text, images), prefer create_video_from_template with a STUDIO-designed template.

Create a Synthesia video from a STUDIO template by substituting its variables (templateData). The server fetches the template first and validates every templateData key against its declared variables — variable names are case-sensitive. Text values are HTML-entity-escaped automatically (Synthesia requirement); media variables accept an uploaded asset ID or a URL. DEFAULTS TO A FREE DRAFT (watermarked); pass render_mode='final' only on explicit approval. Returns a videoId immediately; check progress with get_video.

Retrieve a Synthesia video by ID: render status (in_progress / complete / error / rejected), and once complete, a time-limited download URL, duration, and thumbnail. Use this to check on videos created with create_video or create_video_from_template. Renders take minutes — do not call this in a tight loop.

List videos in the Synthesia account (created via API or STUDIO), newest context first. Paginated: pass the returned nextOffset as offset to fetch more.

Update a video's title, description, visibility, or call-to-action button. The main use is flipping visibility to 'public' to activate the Synthesia share page for a finished video.

PERMANENTLY delete a video from the Synthesia account. Destructive and double-gated: the call is refused unless confirm=true is passed. Only set confirm=true after the user has explicitly confirmed deletion of this specific video.

Upload an image or video to Synthesia and get back an asset ID, usable as a scene background in create_video or as a media variable value in create_video_from_template. Accepted types: image/jpeg, image/png, image/svg+xml, video/mp4, video/webm (GIF and WebP are rejected by Synthesia). Provide a local filePath or a url. TIP: backgrounds and media variables also accept URLs directly — uploading is only needed for non-public files or when a stable asset ID is preferred. For media variables, match the aspect ratio of the element being replaced to avoid stretching.

Upload pre-recorded narration audio (mp3 / audio/mpeg only) to use INSTEAD of text-to-speech: pass the returned ID as scriptAudioId (with scriptLanguage) in a create_video scene. NOTE: Synthesia processes uploaded script audio asynchronously — if video creation fails right after uploading with an error about the asset, wait a moment and retry; processing must complete before the audio is usable.