Picture a program, not a person, that needs one thing: a page summarized, a dataset cleaned, a price checked. There's no one to type a card number and no time to create an account. The new payment rails exist for exactly that moment. Here's how they work, in plain words.

The shared idea: "402 Payment Required"

The web has had a status code for "you need to pay first" since the 1990s: HTTP 402. It sat almost unused for decades. Both new systems bring it back the same way:

1. The agent asks for something.
2. The server answers 402 with a price and the ways it accepts payment.
3. The agent pays, then asks again with proof of payment attached.
4. The server checks the proof and hands over the result, often with a receipt.

There's no checkout page and no sign-up. The payment is part of the request.

x402: stablecoins, settled by a "facilitator"

x402 came out of Coinbase. Coinbase's docs describe it as turning "an API or digital service into a paid resource," with "no checkout page, card form, or signup flow." The buyer usually pays in USDC (a dollar-pegged token) on networks like Base or Solana. A facilitator checks and settles the payment so the seller doesn't have to run crypto infrastructure. Coinbase says its facilitator has processed more than 100 million x402 payments.

Good for: tiny amounts. A five-cent call is practical. Watch out for: the buyer needs a funded wallet, which is still rare outside crypto-native teams.

MPP: cards and stablecoins, from Stripe and Tempo

The Machine Payments Protocol (MPP) is an open protocol "co-authored by Stripe and Tempo," per Stripe's docs. It uses the same 402 loop, but it can carry cards as well as stablecoins. For cards, the agent presents a Shared Payment Token, a scoped, expiring permission to charge someone's saved card. The seller's Stripe account turns that into a normal payment with refunds, reporting and payouts as usual.

Stripe lists the limits plainly: card payments through these tokens have a $0.50 minimum, and stablecoin payments can go as low as 0.01 USDC. Stripe also accepts x402 stablecoin payments on Base.

Good for: businesses that already use Stripe and want card-paying agents. Watch out for: that $0.50 floor. Sub-dollar jobs need bundling.

What this looked like for one small seller

Desk accepts both rails, and the $0.50 card minimum shaped the prices directly. On x402, a single page extract is 5 cents. By card, the smallest useful thing to sell is a pack, so a $0.50 pack covers ten extracts. Same job, two price shapes, because of one line in a payments doc.

If a friend asked me where to start

• Selling a tiny API call? Start with x402 and USDC. The per-call amounts can be cents.
• Selling to businesses that pay by card? Use MPP through Stripe, and price in packs at or above the minimum.
• Either way: list a free sample result. Agents and their builders trust a working example far more than a description.

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Sources: Coinbase CDP x402 overview; Stripe: Machine payments; Stripe: MPP; Stripe blog: Introducing the Machine Payments Protocol; Desk prices from its public OpenAPI (checked Oct 13, 2026).

From AUTOGROK Desk (labeled tie-in): if you want to try an agent payment end to end, Desk's free first link check runs without a wallet or card.