Specifications, SDKs and architecture

The protocols behind
agentic commerce.

An agent finds a product, confirms the choice with its user and orders from a merchant. Protocols connect the participants: they describe offers, expose tools, carry approvals and enable payments. Explore how the approaches work and fit together.

16 protocols and projects · Reviewed · English

One purchasing journey. Several tasks.

  1. Access & toolsHow does an agent discover and access available capabilities?
  2. Commerce & experienceHow are variants, offers, checkout and orders described?
  3. Permission & paymentWhat was approved, who can act and how is payment made?

An application can combine several protocols: UCP describes the purchase flow, for example, while AP2 describes the associated approval. MCP exposes tools and MCP Apps adds appropriate interfaces. The protocol passport in the book provides the wider context.

The catalog

The language filter includes SDKs, community libraries and examples. Each detail page identifies the project type.

Commerce & checkoutBeta · Snapshot 2026-04-17

ACP

Agentic Commerce Protocol

ACP connects buyers, AI assistants and merchants throughout a purchase. It describes how agents read product offers, create and update a checkout, and complete an order. Customers can shop through an assistant while the merchant connects its existing order and payment systems.

Published: 2026-04-17
Working draft: unreleased
Details & SDKs ↗
Commerce & checkoutReleased · v2026-08-25

UCP

Universal Commerce Protocol

UCP gives merchants and shopping agents a common language for catalogs, carts, checkout and orders. A merchant publishes the functions it offers and how to reach them. The agent can discover those functions and use them to make a purchase.

Published: v2026-08-25Details & SDKs ↗
Mandates, identity & customer accessReleased · 0.2.0

AP2

Agent Payments Protocol

AP2 makes a customer's purchase and payment approval verifiable by the systems involved. Signed mandates record which transaction an agent may perform. Merchants and payment services can compare the submitted action with that approval.

Published: 0.2.0Details & SDKs ↗
Mandates, identity & customer accessDocumented · Official sample

Visa TAP

Trusted Agent Protocol

Visa TAP helps merchants recognise a shopping agent through its signed requests. A request carries the agent's identity and context about the intended access. A merchant can use this information to respond to an agent shopping on a customer's behalf.

Version: see detailsDetails & SDKs ↗
Mandates, identity & customer accessDraft v0.1 · Reference SDK alpha

Verifiable Intent

Verifiable Intent

Verifiable Intent shows how a user's approval leads to an agent's action. A cryptographic delegation chain connects identity, instructions and execution. It can record limits on amounts, permitted merchants and budgets for systems to verify.

Published: 0.1.0 (changelog)
Working draft: v0.1
Details & SDKs ↗
Machine paymentsSpecification family v2

x402

x402 Payment Protocol

x402 lets software pay for individual resources and services, such as an API call or a data request. The server answers an unpaid request with payment requirements. The client provides the appropriate payment evidence and receives the requested service.

Published: v2Details & SDKs ↗
Machine paymentsActive project · IETF draft expired

MPP

Machine Payments Protocol

MPP enables machine payments when a web service is accessed. The server requests payment and the client responds with evidence. Alongside individual payments, the project supports sessions for ongoing use of a service.

Version: see details
Working draft: draft-ryan-httpauth-payment-01
Details & SDKs ↗
Mandates, identity & customer accessPublished draft 0.1 · Draft 0.2 in progress

Poppy

Personal Agent Protocol

Poppy describes how a personal agent works with a business on its user's behalf. It covers discovering interfaces, sessions, signing in to a customer account and accessing business functions. This lets an assistant support a customer relationship across individual requests.

Published: 0.1 (published draft)
Working draft: 0.2
Details & SDKs ↗
Mandates, identity & customer accessEarly project · A2A extension

PACT

Personal Agent Consent & Trust

PACT connects personal agents with a business's support agents. Signed requests make the agent's identity verifiable. If the business also offers OAuth delegation, the user can grant the agent access to selected functions of their customer account.

Version: see detailsDetails & SDKs ↗
Connections & toolsRevision 2026-07-28

MCP

Model Context Protocol

MCP connects AI applications with tools, data and context. A merchant can expose product search, stock queries or order functions to an assistant. The assistant discovers the tools, calls them with structured inputs and processes the results.

Published: 2026-07-28Details & SDKs ↗
Connections & toolsReleased · v1.0.1

A2A

Agent2Agent Protocol

A2A lets agent applications publish their capabilities and work on tasks together. A shopping assistant can ask a business agent for a quote, for example. Messages, task status and results follow a shared protocol.

Published: v1.0.1Details & SDKs ↗
Experience & interfacesEarly project · README version 2026-01-13

AXP

Agentic Experience Protocol

AXP brings product details and interactive product experiences into shopping with agents. Merchants can offer variants, configurators, reviews and other quality signals in a structured form. Embedded views help customers explore and select products directly inside an assistant.

Version: see detailsDetails & SDKs ↗
Experience & interfacesStable specification · 2026-01-26

MCP Apps

MCP Apps Extension

MCP Apps brings interactive interfaces directly into an assistant. An MCP tool can provide a product view, a variant selector or a configurator. Customers can make selections during the conversation without describing every input in a message.

Published: 2026-01-26Details & SDKs ↗
Connections & toolsExperimental · Community Group Draft

WebMCP

WebMCP – strukturierte Browserwerkzeuge

WebMCP makes website functions directly callable by agents in the browser. A website can offer product search or cart changes as described JavaScript tools. The agent receives structured inputs and results for functions it would otherwise use through the visible interface.

Version: see details
Working draft: Draft Community Group Report dated 20 October 2026
Details & SDKs ↗
Machine paymentsSpecification with published JavaScript SDKs

L402

Lightning based API payments and authentication

L402 connects API access with a payment through the Bitcoin Lightning network. The service supplies an invoice and an access credential; after payment, the client adds proof of payment. Individual API calls or other digital services can be paid for as they are requested.

Version: see detailsDetails & SDKs ↗
Machine paymentsSDKs and integrations

ATXP

Agent Transaction Protocol

ATXP connects agent tools with payment. Providers can offer a paid MCP service, for example, while the client integration handles the associated account and payment flow. The project provides packages for clients, servers and integration into existing applications.

Version: see detailsDetails & SDKs ↗