One Article to Understand x402 and MPP: Two Routes for Agent Payments

Title: Stripe’s MPP vs. x402: What Actually Happened Today
Author: Nick Sawinyh, defiprime.com
Compiled by: Peggy, Blockbeats

Source:

Repost: Mars Finance

Editor’s Note: Regarding how agents make payments, x402 and MPP offer two nearly opposite approaches.

x402 follows a minimal protocol path: embedding payments directly into HTTP requests, implementing request-as-you-go payment in the simplest way. No accounts, no middlemen—more like the open, permissionless design of early internet, suitable for long-tail developers and decentralized scenarios.

MPP, on the other hand, maximizes system capabilities: using sessions, streaming payments, and compliance systems to address high-frequency trading, risk control, and fiat access. It’s not about purity but prioritizes real-world business needs, making it more suitable for enterprise and scaled applications.

Fundamentally, these are two solutions to the same problem: whether to integrate payments into the protocol itself or to build it as a layer within the system.

Therefore, they are not entirely competing but rather covering different segments—x402 addresses open network long-tail needs, while MPP handles high-frequency and commercial traffic. In an emerging agent economy, this differentiation may be inevitable.

Below is the original text:

Since the HTTP status code 402 was defined in the HTTP/1.1 specification in the late 1990s, it has been waiting for a use case. Its meaning is “Payment Required.” The original idea was to embed payment capabilities into the web protocol layer, allowing machines to purchase resources just like requesting a webpage.

But this idea has mostly not been realized. Over the years, this status code has only appeared sporadically in edge cases, such as Shopify rate limiting responses, Apple MobileMe billing errors, etc., but no one has truly built the micro-payment future it implied. Instead, systems like credit cards, subscription paywalls, and API keys have dominated—these are designed primarily for human operators.

Today, two competing implementations of this future have emerged and been released on the same day. Next, I will clarify what they are, how they differ, and why Stripe is betting on both paths simultaneously.

x402: A Simpler Solution

Coinbase officially launched x402 in May 2025, with an almost aggressively minimal approach. The client requests a resource; the server responds with HTTP 402, informing the client how much to pay, which token to use, and on which chain to complete the payment. After paying on-chain, the client attaches the proof of payment to the retried request, and the server delivers the resource.

It’s that simple. No account system, no API key, no subscription mechanism. Just a single HTTP request round-trip with an embedded payment.

Now, Stripe has integrated native support for x402 into its payment system, allowing merchants to accept such payments directly through their existing backend. However, fundamentally, x402 remains a Coinbase-led protocol, governed by the x402 Foundation, co-founded by Coinbase and Cloudflare in September 2025. The protocol is fully open source (Apache 2.0 license) and offers SDKs in TypeScript, Go, and Python.

Supported platforms include Base, Polygon, and Solana for ERC-20 payments. The ecosystem is exploring expansion to Avalanche, Sui, Near, and other chains, though maturity varies.

Regarding adoption data, it’s a bit complex. Coinbase reports that x402 has processed over 50 million transactions via its Agentic Wallet infrastructure. Sounds impressive, but according to Artemis on-chain analysis cited by CoinDesk on March 11, the daily transaction volume is about 131,000, totaling roughly $28,000, with an average payment of about $0.20. About half of these are testing or gamified activities rather than real commercial transactions.

But that’s not necessarily a bad thing. The protocol was designed for a market that doesn’t yet truly exist—a world where AI agents make micro-payments (even below 1 cent) for API calls and data queries. The merchants serving this market are just beginning to emerge.

For example, Google’s Agentic Payments Protocol (AP2, part of the A2A framework) has integrated x402; Lowe’s Innovation Labs demonstrated a demo where an AI agent completes product discovery, research, and ordering in one flow. Meanwhile, World (initiated by Sam Altman) released AgentKit this week, adding human identity verification to x402 wallets.

The core assumption is: if payments are as lightweight as HTTP requests, applications will naturally emerge. Whether this holds remains to be seen.

MPP: A Full-Stack Solution

Stripe and Tempo have taken a different route. The Machine Payments Protocol (MPP) was launched today alongside Tempo’s mainnet. Unlike x402, which is a lightweight overlay on existing blockchains, MPP is designed specifically for high-frequency trading agents.

Its core mechanism is sessions. Instead of initiating a blockchain transaction for each resource request, an agent can authorize a spending limit once and then perform micro-payments within that limit. If you’re an AI that needs to query thousands of data sources per hour, you wouldn’t want to sign and broadcast a transaction each time—that’s what sessions solve.

Tempo is built around this need. It supports tens of thousands of transactions per second, with sub-second confirmation times, and has no native gas token. Users can pay fees directly with stablecoins, avoiding the hassle of buying a random token just to transfer funds.

Another key component is Stripe’s Agentic Commerce Suite, which includes Shared Payment Tokens (SPTs). Not part of MPP itself but an extension mechanism, SPTs allow agents to securely transmit user card or wallet credentials to merchants without exposing sensitive data. These credentials are single-use, time-limited, and can be seen as programmable, self-destructing authorizations. In practice, an agent paying via MPP can use USDC on Tempo or a user’s linked Visa card, or even combine both.

According to Tempo’s launch blog, partners include Anthropic, DoorDash, Mastercard, Nubank, OpenAI, Ramp, Revolut, Shopify, Standard Chartered, and Visa. The Block reports that over 100 services are already listed in the MPP payment catalog, including Alchemy, Dune Analytics, Merit Systems, and Parallel Web Systems. Matt Huang, co-founder of Tempo and Paradigm, told Fortune that the space is still early, and MPP’s design aims for future expansion beyond Tempo to other chains.

Why does Stripe support both?

If you’re already integrated with Stripe, the most practical answer is: you don’t need to choose.

Stripe supports both x402 and MPP through separate integration paths, not as a unified interface. For x402, their documentation covers address generation, on-chain monitoring, and fund settlement to Stripe accounts—you handle the 402 responses, while Stripe manages the underlying cryptographic payment infrastructure. Currently, USDC on Base is supported, with plans to expand.

For MPP, merchants can use the same PaymentIntents API to accept session-based streaming payments.

Stripe’s Agentic Commerce Suite, released in December 2025, builds on both paths. Merchants upload product catalogs, select AI agents, and Stripe handles discovery, checkout, fraud prevention, and tax compliance. Major users include URBN, Etsy, Coach, Kate Spade, and Ashley Furniture; platforms like Wix, WooCommerce, BigCommerce, Squarespace, and commercetools are also integrated.

Their strategy is clear: control the abstraction layer, allowing the underlying protocols to compete freely.

Comparison at a Glance

Overall, both protocols aim to do the same thing: enable machines to pay for resources via HTTP. But the key differences lie in the details:

x402 (led by Coinbase) vs. MPP (Stripe + Tempo)

Standardization: x402 is fully open source (Apache 2.0), driven by the x402 Foundation with participants like Coinbase, Cloudflare, Visa, Google. MPP is an open standard co-developed by Stripe and Tempo, part of Stripe’s Agentic Commerce Suite.

HTTP Mechanism: x402 revives HTTP 402, using the PAYMENT-REQUIRED header and PAYMENT-SIGNATURE for retries. MPP employs a challenge-response scheme using the Payment HTTP Authentication Scheme (IETF draft), binding challenges with HMAC.

Underlying Payment Layer (Rails): x402 is designed to be blockchain-agnostic, supported on Base, Polygon, Solana, with others exploring. MPP is built on Tempo, a payment-optimized L1 supporting 10,000+ TPS, sub-second confirmation, and no native gas token; cross-chain compatibility is a long-term goal.

Payment Methods: x402 uses pure stablecoins, fully on-chain. MPP supports USDC on Tempo plus SPTs (Stripe’s mechanism), enabling hybrid crypto and fiat payments (bank cards, wallets, BNPL).

Settlement: x402 settles on-chain (roughly 200ms to seconds), with Coinbase and facilitators handling verification and settlement. MPP benefits from Tempo’s sub-second confirmation, with Stripe automatically settling and managing compliance.

Merchant Integration: x402 uses open middleware (Express, Hono, Next.js) for self-hosted or facilitator-based setups. MPP integrates directly via Stripe’s PaymentIntents API, with built-in risk, tax, refunds, and reporting.

Core Innovation: x402 emphasizes extreme simplicity, no vendor lock-in—akin to the Unix philosophy in payments. MPP offers high throughput, fiat integration, session-based streaming, micro-payments, and programmable spending via SPTs.

Key Partners: x402 involves Coinbase, Cloudflare, Google (A2A/AP2), Visa, World, Anthropic. MPP’s partners include Stripe, Visa, Lightspark, Anthropic, DoorDash, Mastercard, OpenAI, Shopify, Revolut, Standard Chartered.

x402 is more suited for building open systems: developer APIs, decentralized data markets, or services avoiding reliance on payment processors. Its specifications could be written into a white paper; integration requires just middleware and a wallet address. Its purity is attractive but limits its audience.

MPP is a different paradigm: if your agent needs hundreds or thousands of transactions per session without on-chain overhead, it’s more suitable. Sessions keep most interactions off-chain until final settlement; Stripe’s compliance handles risk and taxes; SPTs enable hybrid payments, including cards and wallets. It’s less elegant but more practical.

Interestingly, they are not entirely rivals. x402 covers open, permissionless scenarios; MPP targets enterprise-scale high-frequency flows. Stripe’s strategy is clear: support both paths, ensuring funds flow into Stripe’s ecosystem regardless of which protocol wins.

Where are we now?

Honestly, there’s almost no large-scale transaction volume yet.

Coinbase’s announcement mentions early partners like Hyperbolic (GPU inference payments) and Anthropic (MCP protocol). Stripe’s blog references agent scenarios based on API calls (e.g., CoinGecko). Tempo’s directory lists over 100 services. Cloudflare’s SDK supports x402 natively, and some small projects on Base L2 are experimenting with it as a payment gateway.

But overall, activity remains limited—small merchant counts, mostly experimental.

This isn’t surprising. Any new payment infrastructure starts this way. The partner list often includes those who have only signed letters of intent or are in early testing.

What’s more important is the heavyweight infrastructure behind it. Stripe processed $1.9 trillion in payments in 2025, up 34% year-over-year. Coinbase, Cloudflare, Visa, Google, and Tempo’s entire partner network are already involved.

The infrastructure is in place. The only question is: in 2026, will AI agents need to conduct large-scale transactions on this infrastructure? Or is this like laying fiber optics in 1998—demand isn’t here yet, but the groundwork is laid.

So, which should you choose?

If you’re building an open, permissionless system—x402 is the natural choice. No registration, no payment provider dependency—just middleware and a wallet. The trade-off: you handle compliance, risk, and fiat settlement yourself.

If you’re already within Stripe’s ecosystem and want to connect agent traffic—MPP is more suitable. Sessions, streaming payments, hybrid fiat+crypto, and full compliance are more like an upgrade than a complete overhaul.

If your only goal is to ensure you can accept payments regardless of protocol—just use Stripe. It supports both.

Finally, HTTP 402 is finally getting its moment. It just took nearly 27 years.