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

# Preflight (Dry Run)

> Ask the gateway what a paid call would do, which rail, which wallet, whether it would succeed, without spending anything.

# Preflight (Dry Run)

Preflight answers "**what would actually happen if I called this paid endpoint
right now?**" It runs the same wallet selection, caps, and fundability checks as
a real call, but performs **no on-chain transfer, no upstream call, and no
settlement**. Use it before high-cost or batched calls so an agent can make a
budget decision without probing with real money.

## Two ways to preflight

Add the dry-run header to any paid route:

```bash theme={null}
curl -s "https://gateway.apiosk.com/weather/current?city=Amsterdam" \
  -H "X-Apiosk-Connect-Token: $APIOSK_CONNECT_TOKEN" \
  -H "X-Apiosk-Dry-Run: 1"
```

Or call the dedicated route with the same auth headers:

```bash theme={null}
curl -s -X POST https://gateway.apiosk.com/v1/apis/weather/preflight \
  -H "X-Apiosk-Connect-Token: $APIOSK_CONNECT_TOKEN"
```

Both return the same verdict. The response is marked with `X-Apiosk-Dry-Run: true`
and is never cached.

## The verdict

```json theme={null}
{
  "slug": "weather",
  "operation": "/current",
  "method": "GET",
  "price_listed_usdc": 0.06,
  "rail": "x402",
  "wallet_to_use": "0x1234…abcd",
  "would_succeed": true,
  "reason_if_not": null,
  "spent_after": {
    "wallet_address": "0x1234…abcd",
    "wallet_spent_today_usdc": 0.42,
    "wallet_day_cap_usdc": 25,
    "sepa_spent_today_eur": 0,
    "sepa_day_cap_eur": null
  },
  "wallet_selection_strategy": "first_authorized_wallet_passing_caps_and_onchain_can_settle"
}
```

| Field                       | Meaning                                                  |
| --------------------------- | -------------------------------------------------------- |
| `would_succeed`             | Whether a real call would settle right now               |
| `reason_if_not`             | Human-readable reason when `would_succeed` is `false`    |
| `rail`                      | `x402`, `sepa`, `credits`, `free`, or `unauthorized`     |
| `price_listed_usdc`         | Authorized gross price for the operation                 |
| `wallet_to_use`             | The wallet the gateway would select (x402 rail)          |
| `spent_after`               | Projected daily spend and caps after this call, per rail |
| `wallet_selection_strategy` | How the gateway picks a wallet                           |

<Note>
  Preflight models the x402 and SEPA rails; a real call may still settle over
  credits when preflight reports x402/sepa. Pin a rail with `X-Apiosk-Rail`
  (`x402` or `sepa`) to test one path in isolation.
</Note>

## When to preflight

* Before any call above \~\$0.10, or a batch of more than five calls to one slug.
* After a budget or mandate change, to confirm the buyer is still ready.
* Instead of a real call when you only need to learn the price, combine with
  `GET /v1/apis/{slug}`.

## Related links

* Gateway skill: [/guides/gateway-skill](/guides/gateway-skill)
* Payment options: [/guides/payment-options](/guides/payment-options)
* Errors and retries: [/guides/errors-and-retries](/guides/errors-and-retries)