Protocol Stack

Industry-standard protocols for secure agent payments. Sardis implements AP2, UCP, A2A, TAP, x402, and ACP for comprehensive agent-to-merchant and agent-to-agent financial operations.

Overview

Sardis implements six complementary protocols for agent payments. Each protocol handles a different aspect of the payment lifecycle — from identity verification to checkout to inter-agent communication.

┌─────────────────────────────────────────────────────────────┐
│                     External Agents                          │
└─────────────────────────────────────────────────────────────┘
                    │   A2A     │    UCP    │   x402
                    ▼           ▼           ▼
┌─────────────────────────────────────────────────────────────┐
│                  Sardis Protocol Layer                       │
│  A2A (messages)│ UCP (commerce)│ x402 (micro) │ ACP (shops) │
│                         │                                    │
│                    ┌────┴────┐                               │
│                    │ AP2/TAP │  ← Verification               │
│                    └─────────┘                               │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│   Bank Transfer │ Virtual Cards │ Stablecoins (optional)     │
└─────────────────────────────────────────────────────────────┘

Protocols

AP2 (Agent Payment Protocol)

Google, PayPal, Mastercard, Visa consortium standard. Mandate chain verification with full intent-to-payment traceability.

UCP (Universal Commerce Protocol)

Standardized checkout flow for AI agents. Cart management, discount application, session tracking, and fulfillment.

A2A (Agent-to-Agent)

Google-developed multi-agent communication protocol. Agent cards, capability discovery, and payment coordination between agents.

TAP (Trusted Agent Protocol)

Cryptographic identity verification for agents. Ed25519/ECDSA signatures, attestations, and trust scoring.

x402 (HTTP Payments)

HTTP-native micropayments via 402 status code. Coinbase-developed standard for pay-per-request APIs. Automatically handled by the Sardis MPP client.

ACP (Agentic Commerce Protocol)

OpenAI's open standard for AI agent commerce. Product feeds, agentic checkout, delegated payments for ChatGPT-native purchasing.

Chain	Tokens	Status
Base	USDC, EURC	Deployed
Polygon	USDC, USDT, EURC	Ready
Ethereum	USDC, USDT, PYUSD, EURC	Ready
Arbitrum	USDC, USDT	Ready
Optimism	USDC, USDT	Ready

Deployed = Contracts live on testnet | Ready = Chain integration complete, pending deployment