System One (legacy)

The TypeSafe-compatible /v1/systemone endpoint, to be deprecated soon in favor of the OpenAI-compatible /v1/decisions

Deprecated soon

/v1/systemone will be deprecated soon in favor of the OpenAI-compatible /v1/decisions endpoint. It keeps working for existing integrations, but it serves TypeSafe models (Jev) only and gets no new models — gpt-6-luna-decisions and future decision models are available on /v1/decisions only. Jev works on /v1/decisions at the same price; see Migrating from /v1/systemone.

LLMGateway exposes a TypeSafe-compatible /v1/systemone endpoint for System One models: models that read a state, answer questions you name, and return typed decisions with calibrated probabilities. There is no free-form text in the response — every answer is a value your code can branch on directly.

New integrations should use /v1/decisions instead. Requesting a non-TypeSafe decision model here returns a 400 pointing you at /v1/decisions.

For the full request and response schema, see the API reference.

Endpoint

POST https://api.llmgateway.io/v1/systemone

Question types

Every question has a type, instructions, and — for choice and score — its own criteria. Answers come back under the ids you chose.

Type	Ask	Answer
`noul`	A yes/no question	`noul`: probability the answer is yes, 0 to 1
`choice`	One option from a set you define	`choice`, `probabilities` per option, `confidence`
`score`	A rating across ordered levels	`score` (can land between levels), `probabilities`, `legend`, `confidence`

cURL

curl -X POST "https://api.llmgateway.io/v1/systemone" \
  -H "Authorization: Bearer $LLM_GATEWAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "jev-1.13.0",
    "state": "Help! My payouts have been failing for 3 days.",
    "questions": {
      "department": {
        "type": "choice",
        "instructions": "Which team should handle this?",
        "criteria": {
          "billing": "Payments, invoicing, refunds",
          "technical": "Bugs, outages, integrations",
          "sales": "Pricing, upgrades, new accounts"
        }
      },
      "is_urgent": {
        "type": "noul",
        "instructions": "Does this convey urgency?"
      },
      "impact": {
        "type": "score",
        "instructions": "Rate the operational impact.",
        "criteria": ["None", "Limited", "Critical"]
      }
    }
  }'

{
	"model": "typesafe/jev-1.13.0",
	"answers": {
		"department": {
			"type": "choice",
			"choice": "billing",
			"probabilities": { "billing": 0.88, "technical": 0.12, "sales": 0.0 },
			"confidence": 0.81
		},
		"is_urgent": { "type": "noul", "noul": 0.95 },
		"impact": {
			"type": "score",
			"score": 1.9,
			"legend": { "0": "None", "1": "Limited", "2": "Critical" },
			"probabilities": { "0": 0.0, "1": 0.1, "2": 0.9 },
			"confidence": 0.88
		}
	},
	"usage": { "input_tokens": 318, "output_tokens": 34 }
}

The model field reports the pinned model that answered, prefixed with the provider it was served by. Provider aliases that move between releases (for example jev-latest) are accepted and resolve to the pinned version, so a request is always billed and logged against the version you can read prices for.

Request fields

Field	Type	Description
`model`	`string`	Decision model to use. Optionally prefixed with a provider (`typesafe/…`).
`state`	`string \| object \| array`	The content to evaluate. Structured data lets questions reference fields.
`questions`	`map<string, Question>`	At least one typed question, keyed by ids you choose.

Deciding in code

The point of a typed answer is that the policy stays in your code, not in a prompt. Threshold the probability, and use confidence as a second axis to send uncertain cases to a human instead of acting on a coin flip:

const res = await fetch("https://api.llmgateway.io/v1/systemone", {
	method: "POST",
	headers: {
		Authorization: `Bearer ${process.env.LLM_GATEWAY_API_KEY}`,
		"Content-Type": "application/json",
	},
	body: JSON.stringify({
		model: "jev-1.13.0",
		state: ticket,
		questions: {
			department: {
				type: "choice",
				instructions: "Which team should handle this?",
				criteria: { billing: null, technical: null, sales: null },
			},
			is_urgent: { type: "noul", instructions: "Does this convey urgency?" },
		},
	}),
});

const { answers } = await res.json();

if (answers.department.confidence < 0.7) {
	await queueForTriage(ticket);
} else {
	await route(ticket, answers.department.choice, {
		priority: answers.is_urgent.noul > 0.8 ? "high" : "normal",
	});
}

Ask everything you might need in one request: the state is read once and every question is evaluated against it, so a batch of questions costs far less than one request each — including speculative questions you only read when another answer makes them relevant.

Decision models are billed on input tokens only — the state plus every question. Output tokens are free, since the response is a set of values rather than generated text. Question text counts as input on every call, so a large rubric has a real per-request cost.

Decision models only work on /v1/decisions and /v1/systemone. Requesting one on /v1/chat/completions returns a 400 pointing you at the right endpoint, they cannot generate text or call tools, and they are not available in the playground. /v1/systemone takes text or JSON state only; image input is available on /v1/decisions for models that support it.