AP2 Protocol

Agent Payment Protocol (AP2) — the Google, PayPal, Mastercard, and Visa consortium standard for secure agent payments. Sardis verifies the full Intent → Cart → Payment mandate chain with signature validation and replay protection.

Mandate Chain

AP2 uses a three-step mandate chain to ensure that every payment traces back to an explicit user intent:

IntentMandate ───▶ CartMandate ───▶ PaymentMandate
   (User)           (Merchant)         (Signed)
      │                  │                 │
      │ "I want to buy"  │ "Here's cart"   │ "Approved"
      ▼                  ▼                 ▼
                  Sardis Verifier
            • Chain integrity check
            • Signature validation
            • Policy enforcement

Python

from sardis import SardisClient

async with SardisClient(api_key="sk_...") as client:
    # Create intent mandate
    intent = await client.mandates.create_intent(
        agent_id="shopping-agent",
        max_amount_minor=50_000_000,
        allowed_categories=["saas"],
    )

    # Execute payment from cart
    result = await client.payments.execute_mandate(cart.id)
    print(f"Transaction: {result.tx_hash}")

TypeScript

import { SardisClient } from "@sardis/sdk";

const client = new SardisClient({ apiKey: "sk_..." });

const intent = await client.mandates.createIntent({
  agentId: "shopping-agent",
  maxAmountMinor: 50_000_000,
  allowedCategories: ["saas"],
});

const result = await client.payments.executeMandate(cart.id);
console.log("Transaction:", result.txHash);

Verification

Sardis validates every AP2 mandate chain before executing payment:

Chain integrity — Each mandate references its parent
Signature validation — All mandates cryptographically signed
Amount bounds — Cart total must not exceed intent max amount
Replay protection — Mandate cannot be executed more than once
Policy enforcement — Transaction must pass Sardis spending policies and compliance checks

AP2 Protocol

Mandate Chain

Python

TypeScript

Verification

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