SHOPSTACKFIELD GUIDE / 02

AI AGENT CHECKOUT

How an AI agent checkout API works.

An AI agent checkout turns a purchase request into a controlled transaction. The agent sends a product URL and purchase constraints. Shopstack runs the merchant checkout, reports a small set of exact statuses, and pauses when it needs help or payment approval. The user approves or rejects the exact amount at a trusted boundary. Messages, activity, and intent do not authorize payment.

RESPONSIBLE ORGANIZATION
Shopstack
LAST CHECKED
CONTROLLED TRACECONTRACT READY
  1. 01queued
  2. 02started
  3. 03help_required
  4. 04approval_required
  5. 05submitting
  6. 06complete

PAYMENT AUTHORITY STAYS OUTSIDE THE MESSAGE CHANNEL.

01

CHECKOUT LIFECYCLE

One request. Eight exact statuses.

Status tells the application what the checkout needs now. A checkout can move to a help or approval state before it reaches a final result.

  1. WAITqueued

    The checkout waits to start.

  2. RUNstarted

    The merchant checkout is in progress.

  3. ASKhelp_required

    The checkout needs information from the user or application.

  4. APPROVEapproval_required

    The final payment waits for separate approval.

  5. SENDsubmitting

    The approved order is being sent to the merchant.

FINAL RESULTS

complete

The merchant checkout completed.

failed

The checkout stopped because it could not continue.

cancelled

The checkout was cancelled.

02

HUMAN CONTROL

Help is not payment approval.

The two pauses have different purposes. Keep them separate in the user interface and in the checkout logic.

A / HELP

help_required

A message can provide missing checkout information. It can answer a question so the checkout can continue.

Messages cannot authorize payment.
B / PAYMENT

approval_required

Final payment approval uses a dedicated, trusted boundary. The checkout must wait for this approval before it submits the payment.

Only payment approval gives payment authority.
03

PROGRESS SIGNALS

Read each signal for its stated purpose.

Shopstack can show more detail between status changes. This detail helps the user understand progress. It does not change who can approve a payment.

STATUS
The current state in the checkout contract. Use it to decide what the application must do next.
ACTIVITY
A bounded progress update. It can describe current work, but it is not payment authority.
INTENT
A mechanical action name and phase. It is not model reasoning, action data, proof of merchant progress, or payment authority.
04

RESPONSIBILITY

Give each part one clear job.

A controlled checkout is easier to review when each system and person has a clear responsibility.

01 / AGENT

Define the purchase.

Send the product URL and purchase constraints.

02 / SHOPSTACK

Run the checkout.

Work through the merchant flow and return the current status.

03 / PERSON

Keep final control.

Provide help when needed and authorize final payment.

05

LIMITS AND EXCEPTIONS

A request is not a completed purchase.

Checkout execution has typed limits. Your application must keep them visible and must handle each state directly.

  • 01

    A maximum amount is a spending ceiling. It is not approval of the final charge.

  • 02

    A checkout can pause for information or for a protected action. The application must handle that boundary.

  • 03

    Only complete means that the checkout was successful.

  • 04

    The final result contains the checkout information that the merchant makes available.

CONTINUE READING

01What is agentic commerce?02Checkout vs browser automation

PRIMARY SOURCES

Read the source material.

  1. Shopstack checkout skillProduct contract and operating guidance
  2. W3C Payment Request API ↗Web payment request standard
  3. OWASP Transaction Authorization ↗Transaction authorization controls

BUILD WITH THE CONTRACT

Add controlled checkout to your agent.

READ THE SETUP GUIDE