---
title: "gpt-6-luna (OpenAI Decisions API): Model Guide and Request Format | System One"
description: "What gpt-6-luna does in the OpenAI Decisions API: typed questions, choices and levels, text and image input. system-one.dev documents this model but does not host it."
canonical: "https://system-one.dev/en/models/openai-decisions"
language: "en"
---

# gpt-6-luna

OpenAI’s decision model, called through the OpenAI Decisions API. Not served by system-one.dev.

**Not available on system-one.dev** — This page documents another vendor’s model. Calls and billing stay on that vendor’s platform; system-one.dev does not serve it.


gpt-6-luna is the model behind the OpenAI Decisions API. Requests go to `POST /v1/decisions` with an `input` field and an array of named questions; responses carry typed decisions rather than generated text. **system-one.dev does not serve this model**, so calls and billing stay in team’s own OpenAI account.


## Where it fits

Use it when the application needs a bounded answer — one option from a list, an ordinal level, or a yes/no probability — and the team already runs on OpenAI. It accepts text and, unlike a text-only decision model, images.

## How its request differs

The field names are not interchangeable with `POST /v1/systemone`. The input goes in `input` (a string, or a user message with text and images), not `state`. Questions are an array whose entries carry a `name`, not an object keyed by question ID. A yes/no question is `type: "predicate"` here and `noul` in the System One format. Choice options are `choices: [{ value, description }]`; ordered levels are `levels: [{ label, description }]`.

## What to expect on cost

Pricing, rate limits and availability are set by OpenAI and change without notice here. This page quotes no credit price because system-one.dev does not meter this model; see OpenAI’s own pricing page for current numbers.

## Model info

- Vendor: OpenAI
- Availability: not served by system-one.dev
- Endpoint: POST /v1/decisions (OpenAI)
- Inputs: text and images
- Status: public beta at the time of writing

## Frequently asked questions

### Can I call gpt-6-luna through system-one.dev?

No. This page documents the model; calls go to the OpenAI Decisions API with an OpenAI credential. Model IDs, prices and limits on system-one.dev are listed in GET /v1/models.

### Is the request format the same as System One?

No. `input` replaces `state`, questions are an array with `name`, a yes/no question is `type: "predicate"`, and options or levels use their own arrays. Port the question definitions rather than copying the body.

### Why keep questions in application code?

Thresholds and business rules must survive a model change. Keep questions, rubric levels and escalation rules in your code, then revalidate thresholds on labelled samples after switching backends.

### Where are current prices?

On OpenAI’s pricing page. system-one.dev does not bill for this model, so no credit price is shown here.

## Official sources

- [Jev alternatives: hosted and open decision models compared](https://system-one.dev/en/blog/jev-alternatives)

Last updated 2026-11-08

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