The Agentic Commerce Protocol is an open standard governing transactions in which an AI agent acts for a shopper against a merchant's systems. It was co-developed by OpenAI and Stripe and released on September 29, 2025 alongside Instant Checkout in ChatGPT, the first implementation (Source: openai.com). The specification is published under the Apache 2.0 licence and maintained jointly by the two companies, which describe it as in beta (Source: stripe.com; github.com).
ACP addresses the merchant-facing half of agent interaction: agent identification and transaction authorization. It sits alongside MCP, which covers the agent-to-tool connection layer, and the two are frequently named together as the emerging agent-permissioning stack.
Design
OpenAI describes three stated design goals: that the protocol work "across platforms, payment processors, and business types"; that merchants integrate "without changing their backend systems"; and that merchants remain "the merchant of record across the purchase journey–from fulfillment and returns to support and communication" (Source: openai.com).
In the Instant Checkout flow, ChatGPT transmits order details to the merchant's backend over ACP; the merchant accepts or declines the order, processes payment through its existing provider, and handles fulfillment and support. OpenAI characterizes the agent's role as "securely passing information between user and merchant, just like a digital personal shopper would." Merchants pay a fee on completed purchases; OpenAI states the service is free to users, does not affect prices, and that Instant Checkout items "are not preferred in product results," though whether Instant Checkout is enabled is one of several factors used to rank multiple merchants selling the same product.
Payment delegation is handled two ways for merchants not on Stripe: Stripe's Shared Payment Token API, or the Delegated Payments Spec within ACP itself. Stripe merchants can enable agentic payments "in as little as one line of code" (Source: openai.com).
The three trust properties OpenAI states for the initial release are that users "explicitly confirm each step before any action is taken"; that encrypted payment tokens are "only authorized for specific amounts and specific merchants with the user's permission"; and that "only the information required to complete the order is shared with the merchant."
Implementation surface
The published developer documentation covers product-feed management through file upload and through three REST surfaces — Feeds, Products and Promotions — that create feeds, retrieve their contents, and upsert partial product and promotion changes. Requests carry Authorization, Idempotency-Key, Request-Id and API-Version headers, the last pinned to a dated version (Source: developers.openai.com).
At launch, Instant Checkout supported single-item purchases for U.S. ChatGPT Free, Plus and Pro users buying from U.S. Etsy sellers, with Shopify merchants including Glossier, SKIMS, Spanx and Vuori described as coming soon; OpenAI said multi-item carts and additional merchants and regions would follow (Source: openai.com). Stripe's Will Gaybrick, President for Technology and Business, framed the work as "re-architecting today's commerce systems and creating new AI-powered experiences" (Source: stripe.com).
Role in the authorization debate
ACP has been invoked in litigation over whether a website operator may exclude agent traffic. In its August 28, 2026 amicus brief supporting rehearing en banc in *Amazon v. Perplexity*, the Software & Information Industry Association stated that many of its AI-developer members "already build to the agent identification and permissioning standards emerging across the industry — including the Agentic Commerce Protocol ('ACP')" and MCP, and that those members "are disadvantaged by Perplexity's evasive conduct" (Brief of the Software & Information Industry Association as Amicus Curiae Supporting Rehearing En Banc — Amazon v. Perplexity (August 28, 2026)). The brief characterizes ACP as specifying "how an agent identifies itself to a merchant and how a merchant signals whether it accepts agent-initiated transactions" — the same function as the user-agent string whose absence was the factual core of that case (Amazon.com Services, LLC v. Perplexity AI, Inc., No. 26-1444 (9th Cir. Aug. 4, 2026) — Opinion).
The position advanced there is that a voluntary identification standard is undercut when a non-adopting agent gains access the adopters forgo. SIIA is a trade association whose members compete with Perplexity, and the argument is its own rather than a finding of any court.
Related protocols
ACP is one of several agent-transaction standards announced in close succession; Google's Agent Payments Protocol (AP2) addresses overlapping ground (Source: metarouter.io). Agent-to-agent transaction layers, "agent passport" proposals and autonomy certificates are treated on Agentic Economy, which anticipates a layer in which agents "discover, authenticate, and negotiate with other agents rather than with human-facing interfaces."
A principles paper published on September 22, 2026 by six banks (ASB Bank, Bank of America, Capital One, Commonwealth Bank of Australia, ING Group and NatWest Group) names no protocol but describes the focus of agentic-commerce development to date as "on protocols, mostly led by payment networks and technology platforms, and concentrated on product discovery, checkout and payment authorization", and states that "some transactions are operating outside of formal protocols". The banks plan a follow-up paper on implementing their five principles "through protocols, and as relevant industry standards and policies"; their interoperability principle asks industry to build interoperability for functions core to the principles while leaving room for innovation on value-added services (Building Trust in Agentic Commerce: Customer-centric principles (six banks, 2026)). The broader practice is treated at Agentic Commerce.
Relationships
- related: Model Context Protocol (MCP) — the agent-to-tool counterpart, named alongside ACP as an emerging permissioning standard
- depends-on: Agentic Economy, Agentic AI
- instance-of: Agentic AI
- related: OpenAI, Amazon v. Perplexity AI, Software & Information Industry Association (SIIA), AI Agentic Browsers
- related: Agentic Commerce, Building Trust in Agentic Commerce: Customer-centric principles (six banks, 2026) — the banks' principles for the transactions such protocols carry