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

# Exact Scheme

> Fixed-price payments where the client authorizes exactly what the seller will charge.

The `exact` scheme is the default and the one most endpoints should use. The seller declares a price, the client signs an authorization for that exact amount, and the facilitator refuses to settle anything else.

## Wire shape

```json theme={null}
{
  "scheme": "exact",
  "network": "stellar:testnet",
  "amount": "10000",
  "asset": { "address": "CBIELTK6...", "decimals": 7 },
  "payTo": "GCKF...",
  "maxTimeoutSeconds": 300
}
```

`amount` is the exact wire-unit price. The `signedAuthEntries` in the `X-Payment` payload must authorize a transfer of that same amount to `payTo` in `asset`, or `/verify` returns `amount_mismatch`.

## Verify and settle

`/verify` checks the signature, the amount, the destination, and the balance. `/settle` transfers exactly `amount` and returns the `txHash`. There is no partial settlement.

## When to use it

* Any endpoint whose cost is deterministic per call.
* Anything charged per-request rather than per-unit-of-work.
* Almost every REST endpoint.

## When not to use it

* LLM completions or any pay-per-token workload — use [`upto`](/payment-schemes/upto).
* Streaming or unbounded outputs where the final size is unknown.

## Related

* [POST /verify](/api/verify)
* [POST /settle](/api/settle)
* [Error & Rejection Codes](/reference/error-codes) for `amount_mismatch`, `insufficient_funds`, `authorization_expired`.