> ## Documentation Index
> Fetch the complete documentation index at: https://docs.opentype.dev/llms.txt
> Use this file to discover all available pages before exploring further.
# OpenType documentation
> OpenType answers typed yes/no, choice and score questions about a JSON state in one model call per run, with a calibrated probability for every answer.
OpenType answers typed questions about a piece of JSON in one model call per run. You send a `state` (a support ticket, a contract clause, a database row) and a set of questions: yes/no (`noul`), one of N (`choice`), or an ordered level (`score`). You get back a probability for every answer you defined, so your code compares numbers to thresholds instead of parsing prose. This page is for developers who are evaluating or integrating the API: it shows one request, the conventions every request shares, and where to go next.
## One request
A decision run is one `POST /v1/runs`. This one asks a single yes/no question about a ticket.
```bash cURL theme={"system"}
curl -sS https://api.opentype.dev/v1/runs \
-H "Authorization: Bearer $OPENTYPE_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: ticket-4822-urgent" \
-d '{
"kind": "decision",
"instructions": "You triage customer support tickets.",
"state": {"ticket": "I was charged twice this month and nobody answers my emails.", "plan": "pro"},
"questions": {
"urgent": {"type": "noul", "instructions": "reply within the hour?"}
},
"max_output_tokens": 16
}'
```
```ts TypeScript theme={"system"}
const res = await fetch("https://api.opentype.dev/v1/runs", {
method: "POST",
headers: {
Authorization: `Bearer ${process.env.OPENTYPE_API_KEY}`,
"Content-Type": "application/json",
"Idempotency-Key": "ticket-4822-urgent",
},
body: JSON.stringify({
kind: "decision",
instructions: "You triage customer support tickets.",
state: { ticket: "I was charged twice this month and nobody answers my emails.", plan: "pro" },
questions: { urgent: { type: "noul", instructions: "reply within the hour?" } },
max_output_tokens: 16,
}),
});
const run = await res.json();
console.log(run.decision.answers.urgent.probability); // P(yes)
```
```python Python theme={"system"}
import os, requests
res = requests.post(
"https://api.opentype.dev/v1/runs",
headers={
"Authorization": f"Bearer {os.environ['OPENTYPE_API_KEY']}",
"Idempotency-Key": "ticket-4822-urgent",
},
json={
"kind": "decision",
"instructions": "You triage customer support tickets.",
"state": {"ticket": "I was charged twice this month and nobody answers my emails.", "plan": "pro"},
"questions": {"urgent": {"type": "noul", "instructions": "reply within the hour?"}},
"max_output_tokens": 16,
},
timeout=160,
)
print(res.json()["decision"]["answers"]["urgent"]["probability"]) # P(yes)
```
The answer to `urgent` comes back under `decision.answers`:
```json theme={"system"}
{"answered_within_labels": true, "label_mass": 0.991, "probability": 0.83, "type": "noul"}
```
`probability` is the probability of "yes". `label_mass` and `answered_within_labels` tell you how much of the model's mass landed on your labels, so you know when a number is trustworthy. Live responses report `decision.model` as `"neon-1.1"`. The [quickstart](/getting-started/quickstart) walks through a full response with all three question types.
## What every request has in common
| | |
| ----------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Base URL | `https://api.opentype.dev`. Every API route is under `/v1/`. |
| Auth | `Authorization: Bearer otsk_...`, an API key you create in the [console](/console/api-keys). See [Authentication](/security/authentication). |
| Idempotency | `POST /v1/runs` requires an `Idempotency-Key` header of 1 to 255 bytes. See [Idempotency](/guides/idempotency). |
| Body | JSON with `Content-Type: application/json`, snake\_case field names, at most 4 MiB for runs and router selections, 1 MiB elsewhere. Unknown fields are refused. |
| Model | **Neon 1.1**. The optional `model` field on decision runs takes `neon-1.1` or `neon-latest`. See [Models and pricing](/getting-started/models-and-pricing). |
| Money | Integers in micro-USD, in fields ending `_micros`. 1,000,000 micros is \$1. |
| Timestamps | UTC strings in exactly `YYYY-MM-DDTHH:MM:SSZ` form, in fields ending `_at`. |
| IDs | Opaque prefixed strings: `run_...`, `key_...`, `req_...`. |
| Request id | Every response carries an `x-request-id` header. Send your own value to have it echoed back. |
| Errors | `{"error": {"code", "message", "request_id"}}`. Branch on `code`. See [Errors](/reference/errors). |
## Start here
Create a key, send a decision run, and read the probabilities in about five minutes.
Sign up, verify your email, and receive \$5 of free credit.
What a run is, its states, what a response contains, and how replays work.
The `noul`, `choice` and `score` types, dependencies, bounds, and answer shapes.
The playground, API keys, usage, and billing in the browser.
Triage, gating, retries, polling, spend control, and production hardening.
Every error code, what triggers it, and what to do next.
Every endpoint, generated from the OpenAPI document.
## Related
* [Quickstart](/getting-started/quickstart) - send your first decision run end to end.
* [Decision runs](/guides/decision-runs) - a full triage example with thresholds and gated questions.
* [Models and pricing](/getting-started/models-and-pricing) - what one run costs and how the arithmetic works.
* [Errors](/reference/errors) - the error envelope and every code the API returns.