MPP: Amount as a number

A deliberately broken MPP endpoint charging 0.0001 USDC on Base Sepolia.

Pick a protocol

x402 uses its own PAYMENT-REQUIRED header. MPP uses the standard HTTP auth framework, with no facilitator.

x402Coinbase. PAYMENT-REQUIRED and PAYMENT-SIGNATURE headers.MPPTempo and Stripe. WWW-Authenticate: Payment, no facilitator.

New to these? Read what x402 and MPP put on the wire.

Pick a network

Testnets only. Nothing here can move real money.

Network

Asset

USDC, 6 decimals

Set the price

Amounts are atomic units of the asset, so no decimal point.

Amount

= 0.0001 USDC

Scheme

Recipient

Defaults to this network's burn address.

Choose a behavior

Compliant by default. Every deviation is named, and never on by accident.

Behavior

The amount is a JSON number, not the atomic-units string the spec requires. A client that does Number(amount) loses precision above 2^53.

Your endpointAmount as a number

/api/mpp?quirk=amount-as-number

Try it

curl -i "https://test402.com/api/mpp?quirk=amount-as-number"

Returns 402 whose amount is a bare JSON number rather than a quoted string.

Response it will return (HTTP 402)

WWW-Authenticate: Payment id="<bound per request -- run the curl to see it>", realm="test402.com", method="evm", intent="charge", request="eyJhbW91bnQiOjEwMCwiY3VycmVuY3kiOiIweDAzNkNiRDUzODQyYzU0MjY2MzRlNzkyOTU0MWVDMjMxOGYzZENGN2UiLCJtZXRob2REZXRhaWxzIjp7ImNoYWluSWQiOjg0NTMyLCJjcmVkZW50aWFsVHlwZXMiOlsiYXV0aG9yaXphdGlvbiIsInRyYW5zYWN0aW9uIl0sImRlY2ltYWxzIjo2LCJwZXJtaXQyQWRkcmVzcyI6IjB4MDAwMDAwMDAwMDIyRDQ3MzAzMEYxMTZkREVFOUY2QjQzYUM3OEJBMyJ9LCJyZWNpcGllbnQiOiIweDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDA0MDIifQ", expires="2026-01-01T00:05:00Z"

{
  "type": "https://paymentauth.org/problems/payment-required",
  "title": "Payment Required",
  "status": 402,
  "detail": "test402 challenge",
  "note": "test402 scenario. quirk=amount-as-number"
}