# Clef Decision (Jev-compatible)
URL: /docs/experiments/clef-decision
> Jev / System One API-compatible decision model on Workers AI - Clef & Clef-Flash return probabilities for noul/choice questions without free-form text
Tags: ai, workers-ai, decision-model, jev, systemone, clef, agents, classification, structured-output
Bindings: AI
Markdown: /llms.mdx/experiments/clef-decision/content.md
**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.
## Features [#features]
* 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 Reference [#api-reference]
### `POST /decision` [#post-decision]
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**
```json
{
"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**
```bash
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**
```json
{
"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 Cases [#use-cases]
* **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
## Limitations [#limitations]
* 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 project [#use-in-your-project]
## Deployment [#deployment]
### Deploy to Cloudflare Workers [#deploy-to-cloudflare-workers]
[](https://deploy.workers.cloudflare.com/?url=https://github.com/shrinathsnayak/cloudflare-experiments/tree/main/apps/experiments/clef-decision)
The Workers AI binding is automatically provisioned.
### Test your deployment [#test-your-deployment]
```bash
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 Development [#local-development]
```bash
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**
```bash
curl -X POST http://localhost:8787/decision \
-H "Content-Type: application/json" \
-d '{
"state": "test state",
"questions": [{ "type": "noul", "question": "Is this working?" }]
}'
```
## Configuration [#configuration]
### Bindings [#bindings]
This experiment requires a Workers AI binding declared in `wrangler.json`:
```json
{
"ai": [
{
"binding": "AI"
}
]
}
```
No additional secrets required.
## Cloudflare Features Used [#cloudflare-features-used]
* [Workers](https://developers.cloudflare.com/workers/) - Edge compute platform
* [Workers AI](https://developers.cloudflare.com/workers-ai/) - Run AI models at the edge
* Workers AI Clef decision API - Structured decision probabilities
## Next Steps [#next-steps]