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Clef

Provided by: system-one.dev

The highest-priced of the three Clef models. It reads text, JSON, and images and returns a choice, a score, or a yes/no answer.

Model info

  • Provided by: system-one.dev
  • 6 credits per question per 4KB
  • Up to 32 questions · 13MB per request
  • Inputs: text, JSON, and images (PNG, JPEG, WebP)
  • Images: up to 4 · 4MB each · 8MB total
  • Pick one: up to 255 options; Score: 2–10 levels
  • Released 2026-10-01

Uses

  • Classification comparison: When Jev or Clef Flash is not good enough, compare Clef on the same data. See Agent tool routing.
  • Scoring: Use Score against a rubric on an answer or a text-and-image result, as a first-pass evaluation. See Using Score instead of an LLM as judge.
  • Guardrails: Judge whether text and image content breaks a rule, then allow, block, or hand off from a yes/no probability. See Agent guardrails.
  • Agent completion checks: Look at a result or a screenshot and decide whether the task is actually done. See When an agent should stop.

Official sources

Last updated 2026-10-12

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Frequently asked questions

How is Clef different from Clef Flash?
Clef Flash, Clef, and Clef Omni share the same request format and all accept text and images. Clef Flash is the cheapest and fits high-volume, cost-sensitive work. Clef has the highest rate; when Jev or Clef Flash is not good enough, compare Clef on the same data. Compare the rates in each page’s Model info. See What is Clef Flash.
Is Clef a large language model?
No. It does not write a reply or explain its reason. It only returns a choice, a score, or a probability. Use a generative model when you need written content.
Does Clef support Chinese?
Test Chinese results with your own data first.
How is it billed? Is there a free allowance?
By credits, from the number of questions and the request size. See Model info on this page. Details: Pricing. New accounts get 100 free credits on sign-up.