Awesome Agent Payments Protocol

🚀 Curated resources for the agentic commerce protocol landscape — UCP, AP2, A2A, x402, ACP, MPP, trust rails, and interop standards.

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Last updated: 2026-06-07

📋 Contents

Official Documentation
Specifications & Whitepapers
Developer Tools & Starters
Ecosystem & Partners
News & Analysis
Videos & Tutorials
Community

📚 Official Documentation

UCP (Universal Commerce Protocol)

UCP Official Site — Protocol overview, spec, tutorials, and guides
Google Developers: UCP Guide — Integration guide for merchants
UCP GitHub Repository — Specification and documentation
Under the Hood: UCP (Google Developers Blog) — Technical deep dive (Jan 2026)
UCP Launch Announcement (Google Blog) — NRF 2026 announcement
Shopify Engineering: Building UCP — Architecture and layered protocol design
UCP and AP2 — How UCP integrates with AP2 for secure payments (see "UCP and AP2" section on site)
UCP Updates (Mar 2026) — Multi-item carts, catalog queries, identity linking
UCP at Google Marketing Live (May 2026) — Universal Cart across Search, Gemini, and Maps with one-tap checkout via Google Pay

AP2 (Agent Payments Protocol)

AP2 Protocol Documentation — Overview, mandate types, A2A/MCP relationships, and integrations
AP2 Specification
AP2 GitHub Repository — Spec, Python & Android samples
Google Cloud AP2 Announcement
AP2 Roadmap — See roadmap section on official site
AP2 Partners — See partners section on official site
AP2 and UCP — How AP2 provides the payment mandate layer for UCP
Google Gemini Spark — Always-on consumer agent (Gemini 3.5) that queues, monitors, and finalizes purchases under AP2 guardrails (spend caps, merchant allow-lists, explicit approval, permanent transaction trail); announced at Google I/O 2026

A2A (Agent-to-Agent Protocol)

A2A Protocol Site — Official documentation and specification
Announcing Version 1.0 — v1.0 release with enterprise features, signed agent cards, multi-tenancy
What's New in v1.0 — Migration guide from v0.3 to v1.0
A2A Specification — Full protocol spec (JSON-RPC 2.0 over HTTP, gRPC, SSE)
A2A GitHub Repository
A2A Samples
A2A x402 Extension — Payment extension for A2A using x402
A2A Project (Linux Foundation)
ADK A2A Guides

A2A SDKs

Language	Repository	Status
Python	a2aproject/a2a-python	Stable (v0.3); v1.0 alpha in `1.0-dev` branch
JavaScript	a2aproject/a2a-js	Stable
Go	a2aproject/a2a-go	Stable
Java	a2aproject/a2a-java	Stable
.NET	a2aproject/a2a-dotnet	Preview (Microsoft Foundry blog)

x402 (Machine Payments over HTTP 402)

x402.org — Protocol homepage
x402 Developer Docs — Core concepts, quickstarts, guides (docs.x402.org / Mintlify)
x402 GitHub Repository — Spec, SDKs (TypeScript, Python, Go), and examples
x402 Whitepaper (PDF)
Quickstart for Buyers
Quickstart for Sellers
MCP Server with x402 — Guide for monetizing MCP tools with x402
Migration Guide (v1 → v2) — Standardized CAIP identifiers, modular SDK, new headers
x402 V2 Launch Post
Cloudflare Agents SDK: x402 — Built-in x402 support in Cloudflare Workers
Cloudflare Blog: x402 Foundation — x402 Foundation announcement with Coinbase

ACP (Agentic Commerce Protocol)

Note: The ACP spec is currently in beta and uses date-based version snapshots (2025-09-29, 2025-12-12, 2026-01-16, 2026-01-30).

Status update (Mar 2026): OpenAI discontinued the consumer-facing Instant Checkout experience in ChatGPT after a ~5-month trial (low adoption, weak conversion, unresolved sales-tax handling). The ACP protocol itself continues in a narrower form, with OpenAI refocusing on product discovery and ChatGPT apps; Stripe and PayPal remain involved on the payments side. See News & Analysis below.

ACP Spec Site — Protocol overview and interactive demo
ACP: Get Started (OpenAI)
ACP: Key Concepts — Protocol page on OpenAI Developers
ACP: Product Feeds — Product feed spec for merchant integration
ACP: Agentic Checkout Spec — Checkout flow and endpoints
ACP: Delegated Payment Spec — Shared Payment Token and PSP integration
ACP Spec (GitHub) — Spec, RFCs, examples, changelog
OpenAI: Buy it in ChatGPT — Instant Checkout launch post (Sep 2025; consumer feature later discontinued — see News)

Stripe ACP / Agentic Commerce Resources

Stripe: Integrate the ACP — RESTful or MCP server implementation guide
Stripe: Shared Payment Token — Payment primitive for agentic flows
Stripe Blog: Developing an Open Standard for Agentic Commerce

MPP (Machine Payments Protocol)

MPP Official Site — Protocol overview, SDKs, and quickstart
Stripe: Machine Payments with MPP — Implementation docs (crypto + fiat via PaymentIntents)
Stripe Blog: Introducing MPP — Launch post (Mar 2026)
Cloudflare Agents Docs: MPP — MPP integration in Cloudflare Workers
Visa: Card Specification & SDK for MPP — Openly available, processor-agnostic card-based MPP spec + SDK; passes tokenized card credentials through MPP workflows; ties into Visa Intelligent Commerce and Trusted Agent Protocol (2026)
IETF Draft: Payment HTTP Authentication Scheme — See spec link on mpp.dev

MPP and x402: MPP is backwards-compatible with x402. The core x402 exact-payment flows map directly onto MPP's charge intent, so MPP clients can consume existing x402 services without modification. MPP additionally supports session (streaming/pay-as-you-go) payments, recurring payments, and microtransactions across stablecoins, cards, and bank transfers.

AMP (Agentic Mobile Protocol)

Ant International: AMP Launch (Business Wire) — World's first open-sourced agentic payment framework for mobile surfaces (digital wallets, super apps, banking apps, wearables, in-car), announced Apr 28, 2026
Connects LLMs, platforms, and merchant agents to 4.4B+ digital wallet users via Alipay+; cuts agent-to-wallet linking steps ~50% vs card binding; per-transaction money-back guarantee for account-takeover cases

ERC-8183 (Agentic Commerce Escrow)

ERC-8183 Specification — Official EIP
ERC-8183 Discussion — Ethereum Magicians thread
ERC-8004 Specification — Companion identity + reputation registries that ERC-8183 contracts can write feedback to on settlement

ERC-8183 vs x402 / MPP: Where x402 and MPP settle instantly per request (good for stateless metered access), ERC-8183 is the on-chain escrow standard for service-delivery between agents — cases where the deliverable can't be verified by HTTP 200 and a neutral Evaluator may need to adjudicate. Lifecycle: createJob → approve → fund → submit → complete | reject. Stablecoin-denominated, 3-way fee split (provider/evaluator/platform) enforced by the contract, refund-on-expiry, native composition with ERC-8004 reputation feedback on settlement.

Network Trust Rails for Agents

Visa Trusted Agent Protocol

Press Release
Cloudflare Press Note
Visa Agentic Ready Program — LatAm & Asia expansion (Apr 2026) — Geographic expansion plus AI-assisted disputes and a Ramp partnership for automated corporate bill pay

Mastercard Agent Pay

Press Release (Sep 2025)
Initial Announcement (Apr 2025)
Agent Pay international expansion, incl. Hong Kong (2026) — Part of Mastercard's push toward an international agentic-commerce network

Identity / Interop

Model Context Protocol (MCP) — Spec & Docs — Standard for AI agent tool interoperability
MCP Specification (GitHub) — Protocol spec repository
MCP Registry (Preview) — GitHub MCP Registry for discovering MCP servers
Web Bot Auth — Architecture Draft (IETF) — Agent identity via HTTP Message Signatures
Web Bot Auth — Directory Draft (IETF) — Directory for verified bot identities
Web Bot Auth (Cloudflare Developer Docs)
ZKProofport — Zero-knowledge proof generation for AI agent identity. Lets agents prove Coinbase KYC, Country, Google OIDC, Google Workspace, or Microsoft 365 affiliation via x402-paid TEE proving on Base. ERC-8004 registered, A2A compatible. NPM: @zkproofport-ai/mcp. Reference app: OpenStoa (1st place — The Synthesis Hackathon 2026)

📄 Specifications & Whitepapers

x402 Protocol

A2A & AP2

A2A v1.0 Specification
AP2 Specification
UCP Specification — Full spec at ucp.dev

ACP

ACP Spec (GitHub) — Versioned snapshots (2025-09-29 through 2026-01-30)

MPP

MPP Overview & Spec — Protocol specification and payment flow documentation
IETF Payment HTTP Authentication Scheme — See spec link on mpp.dev

ERC-8183 / ERC-8004

ERC-8183 — Agentic Commerce — On-chain escrow standard for agent-to-agent service delivery (lifecycle, fee splits, evaluator role, expiry refund)
ERC-8004 — Trustless Agents — On-chain identity and reputation registries for autonomous agents (signed feedback, scoring rules hash, ERC-1271 contract signatures)

Web Bot Auth / Agent Identity

Research Papers

"Towards Multi-Agent Economies: A2A + x402 Micropayments" — Proposes ledger-anchored identities with x402 for A2A micropayments

🛠 Developer Tools & Starters

UCP Implementation

UCP GitHub Repository — Spec, SDKs (Python, JavaScript), and reference implementations
UCP Python Sample — See samples/ in the repo
Google Merchant UCP Integration Guide

AP2 Implementation

AP2 Python & Android Samples

x402 Implementation

Quickstarts

Quickstart for Sellers
Quickstart for Buyers
MCP Server with x402
QuickNode — Using x402 for Paywalls
Crossmint x402 Starter
x402 Wallet for Claude Desktop — Claude Desktop extension with x402 USDC payments on Stellar and Base. Automatic 402 handling with configurable spending limits.

Live Services

PoolPulse — x402-payable DeFi execution signals API on Base. CLMM slippage, MEV scoring, routing hints for 33 Uniswap V3 + Aerodrome pools. Built with Hono + x402/hono. Pay per call ($0.001–$0.25 USDC). (OpenAPI, Examples)
Coinbase x402 Bazaar — Discovery layer / MCP server exposing 10,000+ x402-payable endpoints that agents can search, discover, and pay for autonomously (also surfaced via AWS Bedrock AgentCore Gateway)

SDKs & Libraries

x402 Monorepo (GitHub) — @x402/core, @x402/evm, @x402/svm, @x402/axios, @x402/fetch, @x402/express, @x402/hono, @x402/next, @x402/paywall
x402 Rust crates + Facilitator
x402-proxy — curl for x402 paid APIs. Auto-pays HTTP 402 responses with USDC, with MCP stdio proxy for AI agents

ACP Implementation

MPP Implementation

MPP SDKs — Official TypeScript SDK (mppx) with middleware for Hono, Express, Next.js, Elysia
Stripe: Machine Payments with MPP — Implementation with PaymentIntents
Visa Card Spec & SDK for MPP — Card-based MPP transactions via tokenized network payment tokens settling over existing card infrastructure

A2A Implementation

A2A Samples Repository — Hello-world, multi-agent, and framework-specific examples
A2A Inspector — Validate your A2A agent

ERC-8183 / ERC-8004 Implementation

CardZero — First known production deployment of ERC-8004 + ERC-8183 on Base mainnet. ERC-4337 smart-contract wallet for AI agents with owner-set spending rules, x402 buyer support, and full Job-escrow lifecycle live at api.cardzero.ai/v1/jobs. Source on GitHub; MCP server published as cardzero-mcp; 27-page docs + /llms-full.txt corpus at cardzero.ai/docs.

Agent Frameworks & Managed Platforms

Amazon Bedrock AgentCore Payments

AWS What's New: AgentCore Payments (preview) — Managed surface for agents to pay for APIs, MCP servers, web content, and other agents
AWS ML Blog: Agents that transact (built with Coinbase and Stripe) — Wraps x402 negotiation, wallet auth, stablecoin settlement, and proof delivery; deterministic session spending limits at the infra layer
Coinbase Blog: AgentCore Payments powered by x402
Sample: AgentCore + CloudFront + x402 — Reference demo using Bedrock AgentCore, Strands SDK, and CloudFront

Cloudflare Agents SDK

Agents SDK Overview
x402 in Agents SDK — Built-in x402 support
MPP in Agents SDK — Built-in MPP support
Cloudflare Blog: x402 Foundation

MCP Integration

OpenAI Agents SDK — MCP
Stripe MCP Server — Stripe's MCP tools for agentic commerce

🌐 Ecosystem & Partners

UCP

Co-developed by Google and Shopify. Endorsed by 20+ partners including Etsy, Wayfair, Target, Walmart, Adyen, American Express, Best Buy, Flipkart, Macy's Inc., Mastercard, Stripe, The Home Depot, Visa, and Zalando. (Source: Google Blog, Jan 2026). May 2026: Universal Cart extends checkout across Search, Gemini, and Maps with Google Pay. (Source: Google Marketing Live)

AP2

Officially reported supporters include Shopify, Etsy, Salesforce, Mastercard, PayPal, American Express, Adyen, Worldpay, and 60+ partners total. (Source: AP2 Protocol site)

x402 Foundation

Cloudflare + Coinbase coordinating adoption of x402. The Agents SDK and MCP servers support x402 out of the box. x402 v2 adds modular payment scheme support for EVM and Solana networks. As of mid-2026, AWS Bedrock AgentCore also wraps x402 as a managed payment surface (built with Coinbase and Stripe), and the Coinbase x402 Bazaar exposes 10,000+ payable endpoints. Per Chainalysis, x402 surpassed 100M+ agentic transactions on Base within ~9 months of launch.

ACP

OpenAI + Stripe co-developed ACP. The consumer-facing Instant Checkout experience in ChatGPT was discontinued in early 2026 after a ~5-month trial (low adoption, weak conversion, unresolved sales-tax handling); the ACP protocol continues in a narrower form with OpenAI refocusing on product discovery and ChatGPT apps. ACP remains open to any PSP — Stripe provides the first implementation via Shared Payment Token, with PayPal also involved. (Source: TechCrunch, Mar 2026)

MPP / Tempo

Stripe + Tempo Labs (Paradigm) co-authored MPP. Design partners include Anthropic, DoorDash, Mastercard, Nubank, OpenAI, Ramp, Revolut, Shopify, Standard Chartered, and Visa. Cloudflare supports MPP in its Agents SDK. (Source: Stripe Blog, Mar 2026)

AMP / Ant International

Open-sourced by Ant International and implemented with Alipay+ wallet partners (40+ wallets, 1.8B accounts, 150M merchants). AMP targets mobile-native agentic payments across smartphones, smartwatches, AR glasses, and in-car systems. (Source: Business Wire, Apr 2026)

Agent Trust Rails

Visa's Trusted Agent Protocol and Mastercard's Agent Pay both leverage Web Bot Auth for cryptographically signed agent identity during browse and payment flows. In 2026 both expanded internationally — Visa's Agentic Ready program to Latin America and Asia, and Mastercard's Agent Pay to markets including Hong Kong.

Agent Reputation & Scoring

DJD Agent Score — Behavioral reputation scoring API for AI agent wallets on Base. Scores agents 0–100 across 5 dimensions using on-chain transaction patterns, sybil detection, and gaming velocity checks. x402-native monetization, MCP server distribution, and ERC-8004 compatible. (GitHub)

Analytics & Dashboards

agenteconomy.to — Real-time dashboard tracking AI agent on-chain payment activity across x402, ERC-8004, ERC-8183 (Virtuals ACP), and MPP (Stripe/Tempo) on 8 chains. Aggregated event counter, chain distribution, facilitator share, and time-series charts. Data refreshes every 6 hours. (source)

Payments Networks

Visa — Trusted Agent Protocol; Agentic Ready program (expanded to LatAm & Asia, 2026); card specification + SDK extending MPP to card payments (2026)
Mastercard — Agent Pay (international expansion incl. Hong Kong, 2026); acquired BVNK for stablecoin infrastructure
PayPal — AP2 support; ACP participant; upcoming UCP payment method
American Express — AP2 partner, UCP endorser
Adyen — AP2 integration, UCP endorser
Worldpay — AP2 support
Stripe — ACP co-creator, MPP co-author, UCP endorser
AWS — Bedrock AgentCore Payments (preview), managed x402 + Stripe surface built with Coinbase and Stripe

Stablecoin & Settlement Infrastructure

AllUnity — Launched an agentic payments settlement layer powered by x402; planning a Swedish krona stablecoin (SEKAU, MiCA-regulated e-money token) targeting a June 2026 debut, settling AI-initiated transactions into local bank accounts (CoinDesk)
Fireblocks — Agentic Payments Suite for stablecoin transactions (The Paypers)
Circle + Nium — Partnership to strengthen stablecoin rails for agentic AI payments (American Banker)

AI / Agent Platforms

Google Cloud — AP2 creator, UCP co-developer
OpenAI — ACP co-creator (with Stripe)
Anthropic — MPP design partner
Shopify — UCP co-developer, AP2 & ACP partner
AWS — Bedrock AgentCore Payments (x402 + Stripe), with the x402 Bazaar MCP server via AgentCore Gateway

Crypto & Web3

Coinbase — x402 creator, AP2 partner, AgentCore Payments partner
Tempo Labs — MPP co-author (Paradigm-backed, payments-optimized L1)
Radius Network — x402-compatible stablecoin L1 for agentic micropayments (mainnet launched Mar 2026; sub-second finality, sub-penny fees) (docs)

📰 News & Analysis

Major Launches & Milestones

Amazon Bedrock AgentCore Payments (Preview, May 2026)

Google Gemini Spark (Google I/O, May 2026)

Gemini Spark announced (Yahoo Tech) — Consumer AP2 agent surface with autonomous, guardrailed purchasing
Google I/O 2026 recap (TheTechHacker)

Ant International Launches AMP (April 2026)

Business Wire: Ant International launches open-sourced Agentic Mobile Protocol — Mobile-native agentic payments via Alipay+

OpenAI Discontinues Instant Checkout (Q1 2026)

UCP Launch & Expansion (Jan–May 2026)

A2A v1.0 (2026)

A2A: Announcing Version 1.0 — Enterprise features, signed agent cards, multi-tenancy

MPP Launch (March 2026)

x402 V2 & Adoption (Late 2025 – 2026)

AP2 Launch (September 2025)

OpenAI Instant Checkout & ACP (September 2025)

x402 Foundation (2025)

Cloudflare Blog: x402 Foundation announcement

Network Trust Rails (2025–2026)

Industry Analysis

Security & Standards

🎥 Videos & Tutorials

AP2

Intro to Google Agent Payments Protocol (AP2) — Beginner-friendly introduction
AP2 Overview & Ecosystem Breakdown — Comprehensive ecosystem analysis
Technical Review: AP2 Code Walkthrough (Kotlin) — Code implementation review
AP2 Core Concept: Signed Authorization & Accountability — Short-form explanation
After MCP & A2A, Meet AP2 — Protocol evolution overview

x402

x402 Deep Dive & Demos — Technical walkthrough
x402 Short Explainer — Quick overview

ACP

OpenAI: Buy it in ChatGPT (ACP) — Official product demo

A2A

A2A Protocol Short Course (DeepLearning.AI) — Built with Google Cloud and IBM Research (see repo for link)

💬 Community

Discussion & Support

Google Developers Community: AP2 Introduction
x402 Community FAQ — FAQ & Discord links
A2A GitHub Discussions

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📊 About These Protocols

UCP (Universal Commerce Protocol) is an open standard co-developed by Google and Shopify for agentic commerce across the full shopping journey — discovery, checkout, identity linking, and order management. UCP is transport-agnostic (REST, MCP, A2A) and compatible with AP2 for secure payment mandates. Launched January 2026 at NRF; Universal Cart (checkout across Search, Gemini, and Maps with Google Pay) added May 2026.

AP2 (Agent Payments Protocol) is Google's open protocol for agent-driven payments with verifiable authorization (mandates) and accountability. Its current core focus is card-based payments with mandate-driven authorization. AP2 serves as the payment layer within UCP.

A2A (Agent-to-Agent Protocol) is an open standard under the Linux Foundation for agent interoperability — discovery, communication, and task delegation across agent frameworks and vendors. The v1.0 release (2026) added enterprise features including signed agent cards, multi-tenancy, and version negotiation. The TSC includes AWS, Cisco, Google, IBM Research, Microsoft, Salesforce, SAP, and ServiceNow.

x402 is an open payment standard built on HTTP 402 for machine-native, internet-native payments. Created by Coinbase and coordinated with Cloudflare via the x402 Foundation. Supports stablecoins on EVM and Solana networks. The v2 release (late 2025) introduced CAIP-based identifiers, a modular SDK architecture, and standards-compliant payment headers. By mid-2026 it is wrapped by managed surfaces such as AWS Bedrock AgentCore and had surpassed 100M+ agentic transactions on Base.

ACP (Agentic Commerce Protocol) is an open standard co-developed by OpenAI and Stripe for connecting buyers, AI agents, and businesses to complete purchases. It originally powered Instant Checkout in ChatGPT; the consumer Instant Checkout experience was discontinued in early 2026, while the ACP protocol continues in a narrower form. Currently in beta with date-based version snapshots. Designed to work with any PSP — Stripe provides the first implementation via Shared Payment Token.

MPP (Machine Payments Protocol) is an open standard co-authored by Tempo Labs and Stripe for machine-to-machine payments over HTTP 402. Supports stablecoins, cards, and bank transfers. Offers charge (one-off) and session (streaming micropayment) intents. Backwards-compatible with x402. Based on an IETF-proposed Payment HTTP Authentication Scheme. Launched March 2026.

AMP (Agentic Mobile Protocol) is an open-sourced framework from Ant International for agentic payments on mobile surfaces — digital wallets, super apps, banking apps, and wearables. Implemented via Alipay+, it emphasizes fast agent-to-wallet linking (~50% fewer steps than card binding) and account-takeover protection with a per-transaction money-back guarantee. Launched April 2026.

Trusted Agent Protocol (Visa) / Agent Pay (Mastercard) help merchants and networks recognize cryptographically verified AI agents during browse and pay flows, built on Web Bot Auth (IETF drafts). Both expanded internationally in 2026. In 2026 Visa also released an open, processor-agnostic card specification and SDK extending MPP to card payments.

📄 License

This list is released under CC0 1.0 (Public Domain). No rights reserved.

Keywords: ucp ap2 agent-payments agentic-commerce a2a x402 acp mpp machine-payments-protocol amp agentic-mobile-protocol trusted-agent-protocol agent-pay gemini-spark web-bot-auth mcp stablecoins verifiable-credentials agentcore erc-8183 erc-8004 google-cloud coinbase stripe openai aws tempo