Kling 3 negative prompt and cfg_scale on Sume: fixed, no field

You cannot set a negative prompt or cfg_scale on kling-3 through Sume. The request builder sends the negative prompt "blur, distort, and low quality" and a cfg_scale of 0.5 for every Kling 3 job, and a non-empty provider.options returns 400 unsupported_parameter.

Plan for that if your prompts rely on a custom negative list.

What Sume does expose

The public fields are prompt, duration, resolution, aspect_ratio (text-to-video), frame_images, generate_audio, callback_url and Idempotency-Key. Sume rejects size, seed and a non-empty provider.options with a loud 400, rather than silently dropping them and billing you for a result you did not ask for.

Steer with the prompt instead

Since there is no negative field, describe what you do want in positive terms and name what must stay still. "Locked-off camera, the label text stays sharp and unmoving" does more than a long negative list would. fal's page notes that each Kling 3.0 shot can have its own prompt in a multi-shot storyboard, which Sume does not expose as a field, so one request is one shot.

For text that must stay readable, add the words in post. See on-screen text in Kling 3 and Seedance 2.5.

If you need the controls

If your work depends on provider-level controls, call the provider directly. Sume's value is the shared job model, billing and catalog, and a fixed envelope is part of how that stays predictable. A request that sends an unsupported field gets a clear error, not a quiet different result.

curl -X POST https://api.sume.com/v1/videos \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"kling-3","prompt":"Locked-off shot of a perfume bottle on marble, label stays sharp","duration":5,"seed":7}'
# 400 unsupported_parameter: seed

Retakes instead of seeds

With no seed, each request is a fresh take. Budget two or three takes for a shot you care about, and keep the winner. The post on seed and size 400s explains which fields are refused and why.

Prompt habits that replace a negative list

You can get much of the effect of a negative prompt with plain positive instructions.

• Say what is locked: camera, background, product label.
• Say what moves: one subject, one motion, one speed.
• Avoid piling up adjectives. One clear verb per subject works better.
• Keep text elements out of the generated frame and add them as captions afterwards.