AI agent shops online: purchase intent, limits, evidence

Key points

• A shopping agent buys within the customer's signed purchase intent: items, maximum amount, merchants.
• Merchants verify the agent's origin and authority for the purchase separately.
• Every purchase becomes verifiable as evidence with purchase intent, order and payment.

Starting point

A customer asks her assistant to find and buy a specific pair of running shoes in her size, for at most CHF 160. The agent searches several merchants, finds an offer and pays. For the customer, what counts is that the agent does not buy something more expensive or different. For the merchant, what counts is that the purchase is wanted and not contested later.

Flow with evidence

1. Purchase intent: the customer confirms a signed purchase intent following Verifiable Intent with item, maximum amount and permitted merchants.
2. Search: the agent compares offers; this has no consequences and needs no check.
3. Request to the merchant: the agent signs its requests following Web Bot Auth, and the merchant recognizes the operator.
4. Checkout: the agent creates the purchase, for example through the Agentic Commerce Protocol, and hands over the purchase intent and a limited payment token.
5. Acceptance and receipt: the merchant checks whether item and price match the purchase intent, accepts and confirms the purchase.

Risks and countermeasures

• Wrong item or price: the purchase intent fixes item and maximum amount; deviations show up before acceptance.
• Manipulated offers: hidden instructions on product pages must not lead the agent to other purchases.
• Payment details: the agent receives a network token instead of the card number.
• Contested purchases: purchase intent, order and payment together prove that the purchase stayed within limits.

Roles and responsibilities

• Customer: sets item, maximum amount and merchants and confirms the purchase intent.
• Agent operator: signs requests and keeps purchase intents and tokens protected.
• Merchant: checks origin and purchase intent before acceptance and keeps the evidence.
• Payment service: issues limited tokens and processes the payment.

How the certificate looks

For the purchase of the running shoes for CHF 149, KYA verifies the purchase intent with its layers, the binding to the agent's key and whether amount and merchant were within limits. The verdict is valid, provided the issuers' keys are provided. Had the agent bought a pair for CHF 189, the scope check reports the code amount_exceeds_limit, and the verdict is invalid.

Adoption

Merchants start by admitting signed agents of known operators and require a purchase intent for orders above an amount. The questions from merchants summarize the key points.

Operating metrics

Merchants track the share of agent orders, the rate of orders declined for missing or mismatching purchase intents and the number of contested purchases. If contested purchases fall for agent purchases with evidence, the flow is working.

Frequently asked questions

May an AI agent shop online for me?

If you give it the instruction. This is safe with a signed purchase intent that fixes item, maximum amount and merchants, so the agent cannot buy beyond it.

How does a merchant know the purchase is wanted?

From the customer's purchase intent, which is bound to the agent and names item and amount. The agent's signature alone proves only who is asking.

Does the agent see my card number?

Not in a secure flow. It receives a token that applies only to one merchant or to itself and can be blocked.

What happens if the agent pays too much?

If the amount exceeds the purchase intent, the merchant should decline the purchase. In the certificate, the scope check shows the excess.

What does KYA verify for an agent purchase?

The purchase intent following Verifiable Intent, signed requests following RFC 9421 and, where present, mandate, decision and receipt.

Can an agent trigger returns?

Yes, if the purchase intent or a mandate allows it. Returns are actions with consequences and should be recorded like purchases.

What happens if the merchant cannot verify the purchase intent?

Then it should treat the purchase like an order without evidence, for example with an additional confirmation by the customer.

May the agent order from several merchants at once?

Only if the purchase intent allows it. A total amount across all merchants makes sense, so partial orders do not exceed the limits.

How long does a purchase intent apply?

As long as the customer specifies, for example a few days for a specific purchase. After that, the agent needs a new confirmation.

Sources

1. Verifiable Intent (Mastercard): https://github.com/agent-intent/verifiable-intent
2. Agentic Commerce Protocol: https://www.agenticcommerce.dev/