MPP Charge Intent

One-time payment per request. Similar to x402 but using MPP headers.

Flow

# 1. Agent requests resource
POST /api/mpp/charge
# → 402 with WWW-Authenticate: Payment header

# 2. Agent retries with payment credential
POST /api/mpp/charge
Authorization: Payment base64url({
  "challenge": { ... },
  "payload": { "signature": "0x...", ... }
})
# → 200 OK with Payment-Receipt header

Challenge Header

WWW-Authenticate: Payment
  realm="zeny",
  method="tempo",
  amount="0.01",
  currency="0xfafddbb3...USDM",
  recipient="0xFacilitator..."

Receipt Header

Payment-Receipt: base64url({
  "settled": true,
  "method": "tempo",
  "timestamp": "2026-04-09T12:00:00Z"
})

Endpoint

POST /api/mpp/charge