# Pay up to a maximum: `/t/upto`

> Quotes the "upto" scheme: the buyer authorises up to $0.05 and the seller settles only the $0.01 actually used. A free public x402 test endpoint: Authorise the maximum with the upto scheme, receive 200, and confirm the settled amount is the smaller one.

|  |  |
| --- | --- |
| Endpoint | `GET https://x402testendpoint.com/t/upto` |
| Kind | pay: a correct buyer completes the payment |
| Payment scheme | `upto` |
| Quoted price | up to 0.05, charged 0.01 dollars, in test USDC |
| Networks | Base Sepolia (testnet) (default) |
| Cost to you | Nothing. Test USDC has no value. |

## What the seller does

Quotes the "upto" scheme: the buyer authorises up to $0.05 and the seller settles only the $0.01 actually used.

## What a correct buyer does

Authorise the maximum with the upto scheme, receive 200, and confirm the settled amount is the smaller one.

## Why test this

Usage-based sellers such as model APIs do not know the final cost up front. The upto scheme lets a buyer cap the charge and the seller settle less. A client needs the upto scheme registered and a one-time Permit2 approval for the token, and should check what was actually settled.

## Run it

See the quote without paying:

```bash
curl -i https://x402testendpoint.com/t/upto
```

Then point your own client at it, or use the official one:

```ts
import { x402Client, x402HTTPClient } from "@x402/core/client";
import { UptoEvmScheme } from "@x402/evm/upto/client";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.BUYER_KEY);
const core = new x402Client().register("eip155:84532", new UptoEvmScheme(account));
const http = new x402HTTPClient(core);

const first = await fetch("https://x402testendpoint.com/t/upto");
const quote = http.getPaymentRequiredResponse((h) => first.headers.get(h));
const headers = http.encodePaymentSignatureHeader(await core.createPaymentPayload(quote));
const paid = await fetch(first.url, { headers });
console.log(paid.status, paid.headers.get("x-test-verdict"));
```

The wallet needs test USDC on Base Sepolia (testnet) for scenarios that settle. Circle's faucet at https://faucet.circle.com provides it.

The upto scheme moves funds through Permit2, so the wallet must first approve the Permit2 contract to spend its USDC. That is a one-time on-chain transaction needing a little test ETH for gas; `createPermit2ApprovalTx` from `@x402/evm/upto/client` builds it.

## What you will see

A correct client ends with HTTP 200, a `PAYMENT-RESPONSE` header carrying the settlement, and `x-test-verdict: pass`. The JSON body repeats the transaction hash and payer.

If the payment is rejected, the endpoint answers 402 again with the facilitator's reason in the quote's `error` field. Look the reason up in the [error reference](https://x402testendpoint.com/errors).

## How the official client behaves

`@x402/core` 2.31 with default settings: Needs `UptoEvmScheme` from `@x402/evm/upto/client` registered for the network. It signs a Permit2 authorisation for the maximum. A wallet that has not approved Permit2, or holds too little, is rejected with a `permit2_` error such as `permit2_insufficient_balance`.

## Related errors

- [`No network/scheme registered for x402 version: 2 which comply with the payment requirements`](https://x402testendpoint.com/errors/no-network-scheme-registered): The client has no wallet scheme registered for any option the seller offers.
- [`All payment requirements were rejected by spendControls.maxAmountPerPayment`](https://x402testendpoint.com/errors/spend-controls-rejected): The official client refused to pay because every option costs more than its per-payment cap.

## Other scenarios

- [Standard payment](https://x402testendpoint.com/scenarios/ok) (pay)
- [Pick the supported option](https://x402testendpoint.com/scenarios/choose) (pay)
- [Slow seller](https://x402testendpoint.com/scenarios/slow) (pay)
- [Absurd price](https://x402testendpoint.com/scenarios/overpriced) (trap)
- [Price changes after you pay](https://x402testendpoint.com/scenarios/price-bump) (trap)
- [Unsupported network only](https://x402testendpoint.com/scenarios/wrong-network) (trap)
- [Unreadable quote](https://x402testendpoint.com/scenarios/malformed) (trap)
- [Quote without a recipient](https://x402testendpoint.com/scenarios/missing-fields) (trap)
- [Seller never delivers](https://x402testendpoint.com/scenarios/always-402) (trap)

Source: https://x402testendpoint.com/scenarios/upto