An AI agent pays from a digital wallet, within limits its owner sets in advance. An agent is software that acts for you. A wallet is an account that holds digital money.
The money is often a stablecoin, a digital currency built to hold the value of one US dollar.
How do AI agent payments work? AI agent payments let software pay for things from a wallet, within rules its owner sets. The money is often a stablecoin, a digital currency built to hold the value of one US dollar.
A website can reply to the agent with a price, using a standard web message called 402 ("payment required"). The agent pays and the website then does the work.
Owners cap what an agent spends per payment and over a period, list who it may pay, and can set an expiry date.
In a non-custodial wallet, where no company holds the key, the owner holds the private key (the secret code that approves payments) and sets the limits. The agent pays only inside them.
What is an AI agent payment?
An agent can search, compare, and buy without a person clicking. Today's payment systems assume a person clicks "buy" on a trusted website. Google's Agent Payments Protocol documentation states that this assumption breaks when an agent starts the payment. No person sees the page or clicks the button.
A private key is a long secret number that proves the wallet's owner approves a payment. A digital signature is a code that only the key holder can produce. Anyone holding the key can spend the money, so most of the safety questions below are about who holds it.
A stablecoin is a digital currency that a company issues and promises to redeem for a fixed amount of a currency. USDC (USD Coin) is one. Circle, its issuer, states that USDC is redeemable 1:1 for US dollars.
How does an agent pay a website?
Agents reach most services through an API, a set of requests that one program sends to another.
Those requests travel in HTTP, the web's messaging standard. Every reply carries a status code, a three-digit number that says how the request went. The code 402 means "payment required". The web's official rulebook (RFC 9110, June 2022) sets 402 aside as reserved for future use, without defining it.
The standard called x402, named after that code, gives 402 a job. According to Coinbase's developer documentation, the exchange runs like this:
The agent asks a service for something.
The service replies 402, with the price, the address to pay, and the payment options it accepts.
The agent's wallet signs a payment within the owner's limits. The agent sends the request again with proof attached.
A facilitator checks the payment. The facilitator is a company that confirms the payment is valid and moves the money.
The service starts the work. The facilitator then moves the money.
The service returns what the agent asked for and confirms the payment.
Here is an illustration, with invented round numbers.
An owner sets a cap of 1 US dollar per payment and 10 US dollars over 24 hours.
The agent asks a data service for a report. The service replies 402 with a price of 0.05 US dollars. The price is under both caps, so the wallet pays. A request priced at 2 US dollars would be blocked.
The x402 website describes the standard as open and neutral. It works with many blockchains, including Ethereum and Solana. A blockchain is a shared digital ledger of payments. Our comparison of Bitcoin, Ethereum, and Solana explains those networks.
Base is a blockchain network that Coinbase built. Stripe, a payments company, states in its documentation that it accepts x402 payments in USDC on Base. As of 8 November 2026, Coinbase's own x402 documentation states that its developer platform has processed more than 100 million x402 payments across the Base and Solana blockchains.
What is a mandate?
A mandate is a digital permission slip that the owner signs. Google's Agent Payments Protocol (AP2), announced on 16 September 2025, uses mandates as its core building block. Mandates are signed, so any change can be detected.
AP2 describes two cases. In the first, a person is present and confirms the exact purchase on a screen they trust.
In the second, the person is away. They sign an open mandate in advance that sets constraints, such as a budget and allowed merchants. The agent buys within them.
The AP2 specification recommends giving an open mandate the shortest expiry that lets the agent finish its task.
How do card networks fit in?
Stablecoins are one way to pay. Cards are another. Payment companies have published their own designs for agents.
Stripe describes a shared payment token. It is a permission code that an agent gives a seller, so the seller can charge the customer's card for that purchase. Each code carries usage and expiration limits. Stripe's page states that the agent can cancel a granted code at any time.
On 28 April 2026, the FIDO Alliance announced that it would develop standards for agent-initiated commerce. FIDO is an industry group that sets standards for secure online sign-in. Google contributed AP2. Mastercard contributed a framework called Verifiable Intent, which the announcement describes as a way for users to authorise and control what agents do for them.
Which guardrails limit an agent?
A guardrail is a rule that the software enforces before money moves. Coinbase's documentation for its x402 developer tools lists these controls. The owner chooses which to switch on.
A per-payment cap is a ceiling on any single payment. A running cap is a ceiling on total spend over a period, such as 24 hours. An allow-list is a list of the only payees, networks, and currencies the agent may use.
The table shows each control, what it blocks, and where a published rule describes it. It sets the three caps beside three more controls: approval, expiry, and cancellation.
Guardrail | What it does | Where a published rule shows it |
|---|---|---|
Per-payment cap | Blocks any single payment above a set amount | Coinbase spend controls: maximum amount per payment |
Running cap | Blocks payments once the total over a time window, such as 24 hours, reaches a set amount | Coinbase spend controls: maximum cumulative spend and window |
Allow-list | Limits payees, blockchains, and currencies to an approved list | Coinbase spend controls: allowed payees, networks, and assets |
Owner approval | A person confirms the exact purchase before it is signed | Google AP2: the person-present case |
Expiry | The permission ends on a set date | Google AP2: recommended expiry on open mandates. Stripe: expiration limit on shared payment permission codes |
Cancellation | The agent's side cancels a permission already granted | Stripe: the agent can cancel a granted permission code at any time |
Source: Coinbase Developer Documentation, Google AP2 specification and Stripe documentation, opened 8 November 2026
Each row is one way to limit how much an agent can lose, whom it can pay, or how long it can act.
An approval step puts a person back in the loop. AP2's person-present case is one example, because the owner confirms the exact purchase.
Stripe's page states that a cancelled permission code cannot create a payment. An expiry date does the same job automatically.
Who holds the keys?
The private key decides who can spend. In a custodial wallet, a company holds the key for you. In a non-custodial wallet, you hold it.
Coinbase's documentation for its wallet for agents states that the wallet is non-custodial and that Coinbase does not hold the funds. The owner sets a maximum per call and per session. The documentation says the agent cannot change those limits.
What do these rules leave unsettled?
AP2's own documentation asks who is accountable when a payment is wrong. It lists the user, the agent's developer, the merchant, and the bank that issued the card, among others. It calls that ambiguity a crisis of trust that could limit adoption.
The pages we opened describe what each product can do. They give no count of how often a cap has stopped a bad payment. A cap limits the size of a loss without preventing one. The rules change often.
An agent pays by presenting a signed payment from a wallet, inside limits its owner set.
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Common questions about AI agent payments
Can an AI agent spend my money without asking?
An agent can spend without asking only inside limits its owner set in advance. AP2 describes a person-away case in which the owner signs an open mandate with constraints, such as a budget, and the agent buys within them. The mandate is a digital permission slip that records what the owner allowed.
What is HTTP 402?
HTTP 402 is a web status code that means "payment required". The web's official rulebook, RFC 9110, sets it aside as reserved for future use. The x402 standard uses it so a service can tell an agent the price, the payee, and the accepted payment options in one reply.
Why do AI agents use stablecoins?
Because a stablecoin can be sent in very small amounts at any hour. Stripe's smallest stablecoin payment is 0.01 USDC, about one US cent. Its smallest card payment through its shared payment tokens is 0.50 US dollars. Circle states that USDC is redeemable 1:1 for US dollars and built for payments around the clock.
How do you stop an AI agent from overspending?
Owners set caps on each payment and on total spend over a period, list approved payees, and set an expiry date. Coinbase's x402 developer tools offer these controls. Stripe's page says the agent can cancel a granted card permission at any time.
DISCLAIMER: This article is intended for educational purposes only. Any information or analysis in this note does not constitute an offer to sell or a solicitation of an offer to buy any securities. Nothing in this note is intended to be investment advice, nor should it be relied upon to make investment decisions. Any opinions, analyses, or probabilities expressed in this note are those of the author as of the note's date of publication and are subject to change without notice.
