The Agentic Commerce Protocol Stack
Six protocols across three architectural layers. Click any protocol node to see its coordination partners, or select a layer to filter. Each node links to its Protocol Lab walkthrough and Observatory essay.
For the full analysis of how these protocols coordinate, read Multi-Agent Orchestration (Issue 068).
Commerce Layer
Product discovery, catalogue access, and transaction orchestration. This layer determines how agents find, evaluate, and initiate purchases across merchant ecosystems.
Universal Commerce Protocol
Open, zero-fee commerce protocol backed by Walmart, Target, Shopify, and Etsy. Provides structured product data access and transaction orchestration for any AI agent.
Coordinates With
Agentic Commerce Protocol
OpenAI's commerce protocol pivoted from checkout to discovery after the Instant Checkout failure. Charges 4% commission and integrates with Stripe for payment processing.
Coordinates With
Payment & Identity Layer
Payment authentication, tokenisation, and agent identity verification. This layer governs how agents prove authority to transact and how financial institutions validate delegated spending.
Visa Intelligent Commerce
Visa's AI-native commerce platform with tokenised credentials, real-time fraud scoring, and agent identity verification. Positions Visa as a trust infrastructure provider.
Coordinates With
Mastercard Agent Pay
Live agentic transactions using tokenised credentials and biometric verification. Running production pilots in Latin America with Microsoft Copilot integration.
Coordinates With
Infrastructure Layer
Agent-to-tool connectivity and agent-to-agent communication. This layer provides the foundational protocols that enable agents to access external systems and coordinate with other agents.
Model Context Protocol
Connects AI agents to external tools, APIs, and data sources. The foundational infrastructure protocol that enables agents to access the systems they need to complete tasks.
Coordinates With
Agent-to-Agent Protocol
Enables agents built by different vendors to discover, negotiate with, and delegate tasks to each other. Complementary to MCP - where MCP connects agents to tools, A2A connects agents to agents.
Coordinates With
Coordination Patterns
Three canonical transaction flows that demonstrate how protocols coordinate across layers. Click a flow to highlight the participating protocols in the stack above.
Agent-Initiated Purchase
A shopping agent discovers a product via UCP, authenticates payment through VIC or Agent Pay, and uses MCP to access the merchant's fulfilment system.
Multi-Agent Negotiation
A buyer agent and seller agent negotiate terms via A2A, with payment settlement through Agent Pay and product data validated through UCP.
Cross-Platform Discovery
An agent uses MCP to connect to multiple commerce platforms, queries product catalogues through both UCP and ACP, and coordinates results via A2A.
Trust Propagation Across Layers
The critical design challenge in multi-agent orchestration is not protocol selection. It is trust propagation. When a human delegates a purchase to a shopping agent, that delegation carries specific constraints - budget limits, brand preferences, delivery requirements. These constraints must propagate faithfully across every protocol boundary the transaction crosses.
A purchase that begins in the commerce layer via UCP, authenticates through the payment layer via VIC, and coordinates with other agents through the infrastructure layer via A2A must maintain the original delegation constraints at every handoff. If any protocol boundary loses context, the transaction violates the human's intent - even if each individual protocol executes correctly.
This is the orchestration layer question: who or what ensures that trust, context, and constraints survive the journey across the full protocol stack? The answer will determine whether agentic commerce achieves genuine autonomy or remains a series of disconnected protocol calls.