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An AI agent buys one “Coldplay World Tour - Floor Standing GA” ticket ($120.00), paying in FDUSD on BSC. Each step shows what the agent sends, what the merchant does behind the scenes, and what Prism returns.

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1. Discovery

The agent checks the merchant’s UCP profile. The merchant fetches the current handler definition from Prism and returns it. Agent → Merchant 
GET /.well-known/ucp
UCP-Agent: profile="https://platform.example/ucp/profile"
Merchant → Prism (background) 
GET https://prism-gw.fd.xyz/api/v2/merchant/payment-profile
X-Project-Identify-Token: prism_live_...
Agent receives: 
{
  "ucp": {
    "version": "2026-01-23",
    "payment_handlers": {
      "xyz.fd.prism_payment": [
        { "id": "prism_default", "version": "2026-01-23" }
      ]
    }
  }
}
The agent confirms xyz.fd.prism_payment is present and proceeds to checkout.

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2. Checkout Session

The agent sends their cart. The merchant calls Prism to get x402 payment requirements and returns them in the session. Agent → Merchant 
POST /checkout-sessions
Content-Type: application/json
UCP-Agent: profile="https://platform.example/ucp/profile"

{
  "line_items": [
    { "item": { "id": "ticket_floor_ga" }, "quantity": 1 }
  ]
}
Merchant → Prism (background) 
POST https://prism-gw.fd.xyz/api/v2/merchant/checkout-prepare
X-Project-Identify-Token: prism_live_...
Content-Type: application/json

{
  "amount": "12000",
  "currency": "USD",
  "resource": {
    "url": "https://merchant.example/checkout-sessions/sess_abc123",
    "description": "Coldplay World Tour - Floor Standing GA"
  }
}
Agent receives: 
{
  "session_id": "sess_abc123",
  "payment_handlers": {
    "xyz.fd.prism_payment": [
      {
        "id": "prism_default",
        "version": "2026-01-23",
        "config": {
          "x402Version": 2,
          "resource": {
            "url": "https://merchant.example/checkout-sessions/sess_abc123",
            "description": "Coldplay World Tour - Floor Standing GA"
          },
          "accepts": [
            {
              "scheme": "exact",
              "network": "eip155:56",
              "amount": "120000000000000000000",
              "asset": "0xaB27f55DB008704Ed8098f0dfBCf5e1aA387b9d9",
              "payTo": "0x40a01003f7543a3a3ee64fFB05504173BDb1C4fD",
              "maxTimeoutSeconds": 300,
              "extra": { "name": "First Digital USD", "version": "1" }
            },
            {
              "scheme": "exact",
              "network": "eip155:8453",
              "amount": "120000000",
              "asset": "0x036cbd53842c5426634e7929541ec2318f3dcf7e",
              "payTo": "0x40a01003f7543a3a3ee64fFB05504173BDb1C4fD",
              "maxTimeoutSeconds": 300,
              "extra": { "name": "USDC", "version": "2" }
            }
          ]
        }
      }
    ]
  }
}
The agent extracts config and passes it to the wallet.

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3. Payment Authorization

The agent’s wallet receives the config as paymentRequirements. No HTTP request goes out at this step — everything happens locally inside the TEE. 
Wallet receives:  config.accepts — two options (BSC FDUSD, Base USDC)
Wallet selects:   eip155:56 (BSC), FDUSD — sufficient balance available
Wallet signs:     ERC-3009 transferWithAuthorization inside the secure enclave
Wallet returns:   complete signed x402 payment object
The private key never leaves the enclave. Only the signed authorization exits.

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4. Complete Checkout

The agent submits the signed wallet output verbatim as the credential. Agent → Merchant 
POST /checkout-sessions/sess_abc123/complete
Content-Type: application/json
UCP-Agent: profile="https://platform.example/ucp/profile"

{
  "payment": {
    "instruments": [
      {
        "id": "wallet_bsc_fdusd",
        "handler_id": "prism_default",
        "type": "default",
        "credential": {
          "type": "default",
          "paymentPayload": {
            "signature": "0x...",
            "authorization": {
              "from":        "0xAgentWalletAddress",
              "to":          "0x40a01003f7543a3a3ee64fFB05504173BDb1C4fD",
              "value":       "120000000000000000000",
              "validAfter":  "0",
              "validBefore": "1760000000",
              "nonce":       "0x..."
            }
          },
          "paymentRequirements": { "...": "config from step 2" }
        }
      }
    ]
  }
}
Merchant → Prism (background) 
POST https://prism-gw.fd.xyz/api/v2/payment/settle
X-Project-Identify-Token: prism_live_...
Content-Type: application/json

{ ...credential object verbatim... }
Prism executes the ERC-3009 transferWithAuthorization on BSC, verifies the transfer, and returns: 
{
  "success": true,
  "transaction": "0xe80c...674b",
  "network": "eip155:56"
}
Agent receives: 
{
  "order": {
    "id": "ord_abc123",
    "status": "confirmed",
    "payment": {
      "handler_id": "prism_default",
      "status": "settled",
      "transaction": "0xe80c...674b",
      "network": "eip155:56"
    }
  }
}
The ticket is reserved. 120 FDUSD has settled on-chain to the merchant’s wallet.

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Testing

Use the production Prism gateway (https://prism-gw.fd.xyz) with your own account and small amounts to validate the full flow end-to-end against real on-chain settlement.

Merchant Guide

Step-by-step implementation for the merchant server

Agent Guide

Step-by-step implementation for the agent platform
Last modified on May 5, 2026