The Agentic Commerce Protocol (ACP)
The language of value exchange. If MCP is the browser, ACP is the Visa network.
If MCP is the "USB-C" that lets agents plug into data sources, ACP (Agentic Commerce Protocol) is the secure handshake that lets them exchange value.
MCP allows an agent to see that a pair of shoes costs $100. ACP allows the agent to negotiate that price, prove it has the funds, and settle the transaction without a human typing in a credit card number.
Why Do We Need a Separate Protocol?
You might ask, "Why not just use MCP's tool capability to call a `pay_now()` function?"
Because money is different. Commerce requires a state machine that simple function calls don't capture. A transaction isn't just an action; it's a lifecycle.
The Complexity of Trade
- Negotiation: Prices in an agentic world can be dynamic. "I'll buy 10 if you drop the price by 5%."
- Identity: "Are you really who you say you are? Do you have a high reputation?"
- Non-Repudiation: "You can't claim you didn't order this later." (Requires Cryptography).
- Escrow/Settlement: Ensuring goods are delivered before funds are released.
ACP provides a standardized set of messages for these interactions, sitting on top of lower-level transport layers.
The ACP Workflow: 4 Stages
An ACP interaction typically follows a four-stage lifecycle. Let's trace a transaction from start to finish.
Discovery (Broadcasting Intent)
The Buyer Agent doesn't browse a website. It broadcasts an Intent to the network (or a specific "Intent Mempool").
Negotiation (The Bazaar)
Seller Agents monitoring the network pick up the intent. They check their internal logic (Inventory, Margin) and respond with Offers.
This enables Dynamic Pricing. A seller can offer a discount instantly to clear stock, without changing the public price on their website.
Commitment (The Handshake)
The Buyer Agent selects the best offer. It sends a Commitment message signed with its private key.
This creates a cryptographic contract. Neither party can back out without reputational damage.
Settlement (The Rails)
The payment rails are triggered. ACP is Payment Agnostic.
It could trigger a Stripe Connect transfer, a USDC stablecoin transaction, or a traditional ACH transfer. The protocol just ensures the signal "Payment Complete" is cryptographically verified.
Identity & Trust: DIDs and VCs
In a world of automated agents, how do you know you aren't negotiating with a scam bot? ACP relies on Decentralized Identifiers (DIDs) and Verifiable Credentials (VCs).
The DID (Passport)
Every agent has a unique ID, like did:web:agent.nike.com. This resolves to a public key, allowing anyone to verify messages signed by this agent.
The VC (Visa)
A credential issued by a trusted third party. Stripe might issue a VC saying "This agent has a valid credit card with >$500 limit." The agent can show this proof without revealing the actual card number.
The "Universal Cart"
ACP unlocks a powerful new user experience: The Universal Cart.
Today, you have a cart on Amazon, a cart on Shopify, and a cart on Nike.com. They are disconnected.
With ACP, the "Cart" lives inside your Agent. You can add a pair of shoes from Nike, a book from Amazon, and a vintage lamp from eBay into a single session.
When you say "Buy", your Agent orchestrates three parallel ACP negotiations, settles them all, and gives you a single receipt. The platform lock-in is broken.
Key Takeaways
- ACP manages the lifecycle of a transaction: Discovery, Negotiation, Commitment, Settlement.
- It enables 'Dynamic Pricing' where agents negotiate deals in real-time.
- Trust is established via DIDs (Identity) and Verifiable Credentials (Reputation/Funds).
- ACP enables the 'Universal Cart', decoupling the shopping experience from any single storefront.