YouTube Shorts GenAI tools vs the Sume call behind each one

What can YouTube's GenAI creation tools make for a Short?

YouTube's help page on enhancing Shorts lists a GenAI creation tools option in the Shorts camera that can create video clips, backgrounds, tracks and effects. It sits beside the other camera tools on the page, such as speed, timer, filters, green screen with gallery photos and videos, and a timeline editor. The page says nothing about an API, so the output lives inside the app.

If your workflow is a script, a spreadsheet of topics or a queue of 30 clips, you need the same four building blocks as calls. Sume covers three of them directly and a fourth partly.

The four items, mapped

The right-hand column describes Sume surfaces as the docs read today; it does not claim the two sides produce identical results.

Clips: ask for 9:16 explicitly

In the Shorts camera the frame is already vertical. Over the API you set it yourself. The Video Router example in the docs sends aspect_ratio: "9:16" with resolution and duration, and the docs say limits are per model, so read capabilities from GET /v1/video-router/models instead of assuming one envelope. Auto create controls default to 720p and 8 seconds with 3 to 10 second clips at 16:9 or 9:16.

Gemini Omni Flash 1.1 always generates synced audio, which matters if you plan to caption speech afterwards. The other catalog models differ, so check before you assume the clip has sound.

Backgrounds and tracks

A background for a green-screen style Short is an image. The Image API takes aspect_ratio values including 9:16, and each model only accepts the values its catalog descriptors list. A still dropped into a Timeline 1.0 video[] slot is a static hold, so a generated background can run for a few seconds as its own shot between clips. To show a still and a clip on screen at the same time, timeline compose tiles them with stack or lays the still over the video with overlay.

For the track, Music Router accepts a prompt up to 5000 characters and rejects duration fields. Ask for the length in words, then trim or fade it in the render.

curl -X POST https://api.sume.com/v1/images \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: short-background-001" \
  -d '{
    "model": "bytedance-seed/seedream-4.5",
    "prompt": "Soft pastel studio backdrop, empty centre, no text",
    "resolution": "2K",
    "aspect_ratio": "9:16"
  }'

What the app does that an API call does not

The in-app tools give you a preview, a timeline editor and one-tap publishing from the phone. A Sume pipeline gives you repeatability and files you can store, but you assemble and upload them yourself. Sume's Timeline 1.0 covers the assembly, and the earlier post on Shorts automation walks through generate-then-assemble.

Whichever route you take, label and rights questions are separate from tooling. This post does not cover them; read YouTube's current disclosure guidance before you publish AI-made material.