# Credit

A **credit** is the unit of metering. Every metered response reports what it cost and what remains.

```
X-Credits-Cost: 5
X-Credits-Remaining: 1195
```

## What things cost

| Operation | standard | high_quality | deep_review |
|---|---|---|---|
| Search | 5 | 15 | 60 |
| Chat message | 2 | 6 | 20 |
| Topic search | 4 | 12 | — |
| Extraction, per source | 2 | 5 | — |
| Document ingest | 1 per 10 pages, min 1 | — | — |
| Paraphrase | 1 per 500 words | — | — |
| Detection | 1 per 1,000 words | — | — |
| Citation format | 0 | — | — |

## What is free

Every `GET`: retrieving a resource you already paid for, listing, jobs, usage,
citation styles, and exports. Reads being free is deliberate — poll and paginate
without watching the meter.

## Depth dominates cost

A `deep_review` search costs 12× a `standard` one. Escalate on demand, not by default. See
depth and cost-control.

## Running out

A call that cannot be paid for returns `402 insufficient_credits`. Nothing is partially charged, and
no resource is created. Per-key caps fail the same way while leaving other keys working
(api-keys).

## Related

pricing-and-credits · usage · cost-control · depth