ACP Cart API

Before writing code

Fetch live spec — the Cart API arrived in the 2026-04-17 release, so anything older will not describe it:

1. Fetch https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/releases to identify the current spec version.
2. Fetch the OpenAPI document for that version: spec/<version>/openapi/openapi.cart.yaml in the repo. This is authoritative for paths, headers, and status codes.
3. Fetch spec/<version>/json-schema/schema.cart.json for the Cart object schema.
4. Web-search site:developers.openai.com commerce cart for narrative guidance.

Never write the request/response shapes from memory — read the OpenAPI document.

Conceptual Architecture

What Cart is for

A lightweight pre-checkout phase for item collection, with: