Inside the AMEX trading stack: How purpose contracts and single-use tokens are powering AI transactions

American Express (Amex) is building a system that allows AI agents to make purchases and pay users – but it’s currently only within its payment network, and it still involves a black box that could hinder trust and order.

Amex is already participating in commercial protocol projects, specifically Google’s Agent Pay Protocol (AP2)focused on collaboration. On the other hand, Amex’s Agentic Commerce Experiences (ACE) developer kit taps into something that most protocols don’t currently have: Full transaction control at the payment layer.

But it’s still not entirely clear how it handles authentication. ACE uses a closed system – acting as both the card issuer and the payment network – to ensure agent-led transactions.

Luke Gebb, Amex’s EVP and global head of innovation, told VentureBeat that the company believes the model is a piece of the puzzle.

“What’s been missing so far is the vision of a company like ours: We feel that trust and security are critical to developing this space,” Gebb said. “This is the first time that someone has taken money off the table.”

Amex sits in that interesting space: Unlike other financial institutions or card providers like Chase or Bank of America, Amex can route transactions through the American Express Network. Visa and Mastercard are the most popular payment networks, but these companies do not issue cards themselves and must work with a bank.

A continuous commercial black box

The ACE Kit is just one way to address some of the biggest business issues: trust, control, accountability, authentication, and security.

Buyers generally don’t want crooked agents to run away with their bank accounts and start buying things. Sellers don’t want to be stuck with unpaid items. Banks don’t want to deal with backlogs and fraud opportunities.

Projects like the ACE kit aim to build trust and accountability by verifying the ownership and goals of the agent. This can create a very demanding agent trade.

Amex says it offers verification, too, though the process behind that is unclear. It describes how it performs authentication, although it does not specify at what layer it does it. More traditional systems include a combination of prescriptive testing and dynamic testing, which helps match the intent and outcome of the validation. Amex said agents built with ACE can move users’ shopping carts and check them against the agent’s original intent. However, they did not reveal how this works.

The people who built the commercial ecosystem complain that, despite the steps being taken to create a layer of trust, many black boxes still exist that may prevent mass adoption.

Raj Ananthanpillai, founder and CEO of identity and authentication system provider Trua, told VentureBeat that payment systems and software kits such as Agentic Commerce Suite from Stripe, Google’s Verifiable Intent proof of intent, and the ACE developer kit. "they are very efficient in handling proof, verifiable authorization and bag transport machines, but left upstream human authentication unclear and underdeveloped."

Ananthanpillai continued: "Without a clear, high-security cryptographic link that proves that the agent is acting under the clear authority of a verified individual owner, merchants, issuers, and networks face high risks of abandonment, large chargebacks, unauthorized persons performing financial operations, and fraud."

ACE kit

The ACE developer kit solves several practical problems with commercial agents, Gebb said, and gives developers access to integrated services:

• Agent registration

• Account activation

• Intelligence of purpose

• Payment details

• The core of the cart

First, it deals with agent registration, establishing the identity and trust of both the consumer and the company’s agents. When the transaction begins, the customer’s agent and the seller’s agent can verify each other’s identity and trust that they are dealing with the right business.

Next comes account capabilities, which link a user’s Amex account to their agent and give the agent permission to make, or, in the case of agent trading, buy something.

Intent intelligence creates what Amex calls an intent contract, where the user defines what they want the agent to do. Once the objective is defined, the ACE system generates i The target ID and a Proof of Intent Token that proves to be definitely authoritative if there is a dispute.

Amex handles the actual part of the transaction, where the user pays for the product using a single-use token. ACE establishes payment credentials used for work, responsible for targeting and blocking.

“Once the agent has received the item that the customer requested, such as red shoes, they will call to obtain the payment letters, which are the restricted symbols provided by the card member,” said Gebb. So, for example, if they say they only want to spend $500, that token will not allow the purchase of $600 because it has built-in controls.”

The last piece is cart context and verification, which Gebb said helps banks and brands compare the user’s cart their agent sent to their target.

Amex’s approach shows that in order for commerce to really increase, providers must understand what programs will allow agents to perform and who will be held accountable if something goes wrong.