Agentic Commerce: A Guide to L402, X402, and MPP

Agentic Commerce: A Guide to L402, X402, and MPP

AI agent payments and the 402 Revolution: Why Now?

Back in 1997, when HTTP/1.1 was first defined, the status code 402 Payment Required was introduced… and then basically forgotten. For almost 30 years, it sat there as a placeholder for a financial layer of the web that never really showed up.

That changed with the rise of AI. Traditional payment rails built on monthly subscriptions and 3% + $0.30 fee structures are fundamentally incompatible with the high-frequency, low-value transactions required by autonomous agents. 

Protocols like L402, x402, and MPP are finally bringing this dormant idea to life. They turn the web into something much more dynamic: a global, permissionless marketplace where machines can exchange value as easily as they exchange data.

We’re moving into a world where:

• agents buy and sell services on their own

• APIs are monetized per request

• and payments happen continuously, in the background

Understanding L402, x402, and MPP isn't just a technical choice, it’s a prerequisite for surviving the shift to agentic commerce.

This article helps you explore the leading protocols for AI agent payments. Compare L402, X402, and MPP to understand how to monetize APIs and resources.

Protocol Overviews

L402: The Bitcoin Lightning Standard

Published: In 2020 by Lightning Labs.
Website: github.com/lightninglabs/L402
What makes it special: L402 combines Macaroons (for granular authentication) with lightning invoices. It is uniquely powerful because it allows for truly "stateless" authentication; the payment preimage itself acts as the cryptographic proof of access, meaning the server doesn't need to store a database of API keys to verify a user. Bitcoin on the lightning network is the gold standard for agentic payments: It offers permissionless access with instant, low cost and importantly fully private transactions.   

X402: The Open Stablecoin Protocol

Published: May 2025 by Coinbase; now part of the Linux Foundation.
Website: x402.org
What makes it special: x402 focuses on "Internet-Native" payments using stablecoins (e.g. USDC) across EVM chains s(e.g. Base) and Solana. It introduces the concept of a Facilitator, a middleware that abstracts away the complexity of blockchain settlement. For developers, this means they can accept payments and receive funds in their wallet without ever writing a smart contract or managing gas fees.

MPP: The Machine Payments Protocol

Published: March 2026 by Stripe and Tempo Labs.
Website: mpp.dev
What makes it special: MPP is the "Enterprise-Grade" contender, recently submitted to the IETF. Its standout feature is the native session model. MPP allows an agent to authorize a spending limit upfront and then "stream" thousands of sub-cent micropayments within a single session. It is also rail-agnostic, supporting everything from bitcoin, stablecoins to traditional payment cards.

The Comparison Matrix

Note: This is a current snapshot. These protocols evolve, so check back for updates.
* Actual performance depends on the number of hops and fees between sender and receiver.

Current Usage & Ecosystem Stats

As of March 2026, the adoption curve for 402 protocols is on a growth trajectory. 

L402: While bitcoin payments over the lightning network are private, estimations amount to $1.1 billion in monthly transaction volume in November 2025, spread across 5.2 million transactions beyond mere L402 payments, according to a report from bitcoin financial services company River (source). AI models overwhelmingly prefer bitcoin and digital-native money over traditional fiat (source). 

x402: The protocol has seen growing adoption in the machine economy. In the last 30 days alone, the network has processed ~75.M Transactions with a total payment volume of ~$24M. There are ~94K buyers and ~22K sellers listed or active on x402. (source)
Stripe, AWS, Cloudflare, and Vercel have launched support for x402-gated resources, allowing developers to monetize APIs using these platforms.

MPP: Although only published in March 2026 there are already 181 registered endpoints (source)  and nearly 90 different providers (source) selling services via MPP. Industry heavyweights including Stripe, Visa, Lightspark, and Cloudflare announced support for MPP.

Alby: The Universal Adapter for Agentic Payments

We believe the transition to agentic commerce shouldn't be a headache for developers. Alby acts as the "missing link" between the standard web tools you use today and the autonomous financial layer of tomorrow. Whether you're building an agent that needs to buy data or a service that needs to sell it, we've built the bridges to get you there.

• The Consumer Side: Using the Alby Payment Skill, you can empower your AI agents to autonomously discover and pay for resources across all three 402 protocols. This removes the "payment friction" for agents all while you keep control over the budget.

• The Provider Side: For those looking to sell services, Alby’s Bitcoin x402 Facilitator offers a streamlined way to sell 402-gated resources. PaidMCP helps you to quickly monetize your MCP service. Furthermore, 402 Proxy is an example repo that accepts L402, x402 and MPP payments.

More tools and services are available on https://getalby.com/ai. Stay tuned. There is more to come.

Conclusion: Building for the Agentic Wave

The shift to a machine-first web is already underway. With L402, X402, and MPP, we’re moving beyond clicks and subscriptions toward a far more fluid economy. One powered by microservices and streaming payments.

If you want to see this in action, check out agentic services on lncurl.lol. Developers are already building things like.

• SEO agents that pay for premium keyword data on demand to optimize content in real time

• AI inference services with true pay-per-request. No credits, no top-ups

• On-demand AI artists for generating images and music

• Adaptive infrastructure, where cloud resources are sold dynamically via 402 as usage thresholds are reached

We’re here to help you tap into this shift. The market for 402-gated resources is growing fast. Whether you want to enable your agents to seamlessly consume services across protocols, or monetize your own APIs using these emerging standards, we have the tools and experience to get you there.

Contact us. We’ll help you get ready for the next wave of agentic commerce.