Clef Decision (Jev-compatible)

Clef is Cloudflare's open-source decision model on Workers AI - in the same family as Typesafe's Jev / System One API. Instead of generating free-form text, it takes a state plus typed questions and returns a probability for every allowed answer so agents can act without parsing LLM prose.

This experiment is a deployable Worker reference for @cf/cloudflare/clef and @cf/cloudflare/clef-flash: post a state and noul (binary) or choice (multiple-choice) questions, get structured probabilities back. Existing Jev integrations can switch by changing the endpoint and model.

FeaturesCopy Anchor Link

• Jev / System One-style decision API on Workers AI (Clef and Clef-Flash)
• Binary (noul) and multiple-choice (choice) questions with probability distributions
• No free-form generation - bounded outputs agents can route on immediately
• Stateless edge Worker - under ~60s, no storage required
• Pasteable src/lib/decision.ts core for your own project

API ReferenceCopy Anchor Link

POST /decisionCopy Anchor Link

Call Workers AI Clef or Clef-Flash to answer structured decision questions and return probability distributions. Compatible with Jev-style state + typed questions workflows.

Request body

{
  "state": "Short description of the current state or context",
  "questions": [
    {
      "type": "noul",
      "question": "Will it rain tomorrow?"
    },
    {
      "type": "choice",
      "question": "What color is the sky?",
      "choices": ["blue", "gray", "red"]
    }
  ],
  "model": "@cf/cloudflare/clef"
}

Fields

• state string (required) - Context or state description
• questions array (required) - Array of question objects
  • type string - "noul" (binary) or "choice" (multiple-choice)
  • question string - The question text
  • choices string[] - For choice type, the list of possible answers
• model string (optional) - Model name, defaults to @cf/cloudflare/clef. Also supports @cf/cloudflare/clef-flash

Example request

curl -X POST https://clef-decision.example.workers.dev/decision \
  -H "Content-Type: application/json" \
  -d '{
    "state": "The weather forecast shows clouds moving in.",
    "questions": [
      { "type": "noul", "question": "Will it rain?" },
      { "type": "choice", "question": "When?", "choices": ["today", "tomorrow", "next week"] }
    ]
  }'

Example response

{
  "model": "@cf/cloudflare/clef",
  "state": "The weather forecast shows clouds moving in.",
  "questions": [
    { "type": "noul", "question": "Will it rain?" },
    { "type": "choice", "question": "When?", "choices": ["today", "tomorrow", "next week"] }
  ],
  "answers": [
    { "type": "noul", "probability": 0.73 },
    { "type": "choice", "probabilities": [0.15, 0.65, 0.2] }
  ]
}

Error responses

• 400 - Invalid JSON body or missing required fields
• 502 - Workers AI error

Error codes

• INVALID_JSON - Request body is not valid JSON
• INVALID_REQUEST - Missing or invalid state or questions
• AI_ERROR - Workers AI returned an error

Use CasesCopy Anchor Link

• Agent routing - escalate, auto-resolve, or assign a ticket without a human in the loop
• Jev / System One alternative - drop-in decision model on Workers AI with Clef or Clef-Flash
• Support triage, invoice workflows, and security incident classification
• Multi-step agent graphs that need bounded yes/no or choice probabilities
• Fast edge decisions where LLM free-form text would be slow or hard to parse

LimitationsCopy Anchor Link

• Requires Workers AI binding (must deploy or use --remote locally)
• Question complexity limited by model context window
• Probability outputs are model-generated estimates, not guarantees
• No persistent storage or decision history
• Optimized for structured decision questions - not open-ended chat or free-form generation

Use in your projectCopy Anchor Link

import type { Env } from "../types/env";export type DecisionQuestion =  | { type: "noul"; question: string }  | { type: "choice"; question: string; choices: string[] };export type DecisionModel = "@cf/cloudflare/clef" | "@cf/cloudflare/clef-flash";export type DecisionResult = {  model: DecisionModel;  state: string;  questions: DecisionQuestion[];  answers: unknown;};export async function runDecision(  env: Env,  state: string,  questions: DecisionQuestion[],  model: DecisionModel = "@cf/cloudflare/clef"): Promise<DecisionResult> {  const answers = await env.AI.run(model, {    state,    questions,  });  return {    model,    state,    questions,    answers,  };}

DeploymentCopy Anchor Link

curl -X POST https://clef-decision.your-subdomain.workers.dev/decision \
  -H "Content-Type: application/json" \
  -d '{
    "state": "The weather forecast shows clouds.",
    "questions": [{ "type": "noul", "question": "Will it rain?" }]
  }'

Local DevelopmentCopy Anchor Link

cd apps/experiments/clef-decision
npm install
npm run dev

The Worker runs at http://localhost:8787 with --remote for AI binding access.

Test locally

curl -X POST http://localhost:8787/decision \
  -H "Content-Type: application/json" \
  -d '{
    "state": "test state",
    "questions": [{ "type": "noul", "question": "Is this working?" }]
  }'

ConfigurationCopy Anchor Link

BindingsCopy Anchor Link

This experiment requires a Workers AI binding declared in wrangler.json:

{
  "ai": [
    {
      "binding": "AI"
    }
  ]
}

No additional secrets required.

Cloudflare Features UsedCopy Anchor Link

• Workers - Edge compute platform
• Workers AI - Run AI models at the edge
• Workers AI Clef decision API - Structured decision probabilities

Next StepsCopy Anchor Link