> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fastino.ai/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Use https://docs.fastino.ai/openapi.json as the source of truth for customer-facing routes. For GLiDE decision inference, call POST https://api.fastino.ai/v1/systemone with model fastino/glide. Do not infer undocumented routes. Read API keys from FASTINO_API_KEY and never embed credentials in code, logs, or reports.

# Choice — GLiDE's pick-one-of-many decision primitive

> Ask GLiDE to pick one option from a defined set and get back the selected option, a confidence value, and a full probability distribution.

A **Choice** question asks GLiDE to pick one option from a fixed, caller-defined set of up to 255 named options. The response includes the selected option, a confidence value, and a full probability distribution over every option you defined.

Use a Choice when the answer is one of several unordered categories: which team should handle a ticket, which category a product belongs to, which language a snippet is written in.

## Request

<ParamField body="type" type="string" required>
  Always `"choice"`.
</ParamField>

<ParamField body="instructions" type="string" required>
  The question to evaluate, in natural language.
</ParamField>

<ParamField body="criteria" type="object" required>
  An object mapping up to 255 option keys to description strings, e.g. `{"billing": "Payment or charge disputes", "returns": "Refund or return requests"}`. Both the option names and their descriptions are sent to the model, so write descriptions that separate similar-sounding options from each other.
</ParamField>

<CodeGroup>
  ```bash cURL theme={null}
  curl -s https://api.fastino.ai/v1/systemone \
    -H "X-API-Key: YOUR_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{
      "model": "fastino/glide",
      "state": "Refund request: the receipt is attached, the purchase was 10 days ago, and refunds are allowed within 30 days.",
      "questions": {
        "department": {
          "type": "choice",
          "instructions": "Which team should handle this request?",
          "criteria": {
            "billing": "Payment or charge disputes",
            "returns": "Refund or return requests",
            "shipping": "Delivery or shipping issues"
          }
        }
      }
    }'
  ```
</CodeGroup>

## Response

```json theme={null}
{
  "department": {
    "type": "choice",
    "choice": "returns",
    "confidence": 0.9983415574354015,
    "probabilities": {
      "billing": 0.000576420510560337,
      "returns": 0.9989179779459618,
      "shipping": 0.0005056015434779647
    }
  }
}
```

* `choice` — the option with the highest probability.
* `probabilities` — the full distribution across every option you defined; keys match your `criteria` keys and sum to \~1.
* `confidence` — `top1 − top2`, the probability margin between the best and second-best option, from `0` (two options tied) to `1` (one option has \~all the probability mass). See [Confidence](/concepts/decision-models#confidence) for how to act on it.

## Using the result

```python theme={null}
answer = response["answers"]["department"]

queue_map = {"billing": "billing-team", "returns": "returns-desk", "shipping": "logistics"}
target_queue = queue_map[answer["choice"]]

if answer["confidence"] < 0.5:
    notify("routing uncertain — runner-up may also apply")
```

## Ask every question you need in one call

Evaluate several Choice questions against the same `state` in a single request rather than one request per question — they're answered independently, so adding a question costs tokens but barely changes latency. A support-triage call might ask `department`, `urgency`, and `tone` together instead of three round trips; your code can act on `department` and ignore the rest until it needs them. See [Combining multiple questions](/concepts/decision-models#combining-multiple-questions) for a worked example.

Give the model the full list of real options rather than a shortlist — a Choice question accepts up to 255 options, and each one costs only a few tokens. Add an `other` or `none of the above` option when the input might not cover every case, so GLiDE has somewhere to put the probability mass instead of forcing a bad match onto one of your named options.

## Related

* [Noul](/concepts/glide-noul) — a yes/no decision with a probability
* [Score](/concepts/glide-score) — rate on an ordered scale
* [Decision Models](/concepts/decision-models) — primitives overview, limits, and the full request contract
* [GLiDE](/concepts/glide) — what GLiDE is and when to use it