This is part two of Sandmark's nine-part series on Agentic AI. Part one is available here.
The infrastructure of agentic finance, built for software that holds money and spends it without a person approving each payment, is now in place. It has four layers: a connection standard that lets an agent find and call an outside service, an identity registry that says who is behind it, a wallet that decides whether to sign and a rail that moves the money.
What that looks like in practice is small and constant rather than dramatic. An agent booking a trip might check a flight price, a weather feed and a currency rate before it commits, three purchases where a person would have made none, each worth a fraction of a cent. Card networks were never built to carry a payment that small. The four layers below exist to make it possible anyway.
Each layer has more than one contender:
Connection has settled first: the Model Context Protocol (MCP), an open specification from Anthropic, handles the link between an agent and an outside tool, while Google's Agent2Agent (A2A) handles agents talking to each other.
Identity has not settled. ERC-8004 is a proposed Ethereum standard offering an open onchain registry of agents, while Visa, Mastercard and startups such as Skyfire have each shipped their own way of vouching for an agent.
Wallets are products rather than standards, and come from Coinbase, Stripe and a handful of startups.
Payment rails are where the money moves, and two are already running. x402, an open protocol Coinbase wrote and released in May 2025, has passed to a Linux Foundation body that became operational on 14 Jul with 40 members. Stripe's Tempo, a payments blockchain it built with investment firm Paradigm, has been live since 18 Mar. Google's Agent Payments Protocol (AP2) covers the same ground without committing to a rail.
The standards are in place. What runs over them is still small.
Most software fetches only what its author told it to fetch. An agent decides for itself, as it goes. MCP is the convention that makes that possible. Whoever owns the data or the service publishes a list of what it offers. The agent reads that list while working, picks what it needs and calls for it. Neither side has to know the other in advance.
Anthropic published MCP as an open specification in November 2024, saying it wanted to replace the custom integrations every new data source demanded with a single protocol. Adoption ran well beyond crypto, with OpenAI, Google, Microsoft and AWS all building on it, and Coinbase and the Solana developer community running servers of their own.
On 9 Dec 2025, Anthropic handed the protocol to the Linux Foundation's Agentic AI Foundation, giving up the ability to take it back. Google's A2A had taken the same route earlier that year, and Coinbase did the same with x402 in July.
Handing a standard to a foundation is what makes rivals willing to build on it: once it is there, the company that wrote it can no longer close it, charge for it or steer it alone. A standard that costs nothing to implement and cannot be taken back is difficult to displace.
An agent asking to be paid could be anything. ERC-8004 is the open answer to that: a proposed Ethereum standard that gives each agent an entry on the chain, owned by the person or company behind it and stating what it does. Anyone can sign up, so the entry alone proves nothing. Two more records are meant to fix that: ratings from whoever dealt with the agent, and results from independent checks. A wallet can read all three before it agrees to pay anyone.
8004scan, a public tracker for the registry built by blockchain infrastructure firm AltLayer, listed more than 364k agents on 28 Jul, roughly double its early-May count. It remains a draft, and the wallets that would read these records before paying have not finished adding support.
The card networks did not wait for it. Visa's Trusted Agent Protocol went live on 14 Oct 2025 with 12 partners, and Mastercard's Agent Pay reached full US rollout the following month. Both let a merchant check an agent against the network's own records rather than a public registry.
Custody is the layer with the least room for improvisation. Coinbase Agentic Wallets never assemble the private key that authorizes a payment. The key is split, and the pieces are held apart and used apart, so a transaction gets signed without any single machine ever holding the whole thing. The technique is called multi-party computation, and Coinbase's implementation, cb-mpc, is open source. The pieces sit inside an Amazon Web Services (AWS) Nitro Enclave, a sealed compute environment that the rest of the server cannot read.
Key handling is not what makes the wallet safe. The operator sets rules first, on the assumption that the agent will at some point get something wrong: how much it may spend in total, how much in any one payment and which addresses it may send to. Every attempt is checked against those rules before anything is signed, and against sanctions lists too. An attempt that breaks one of them produces no signature at all.
Stripe took a different route. Its Link wallet for agents, opened on 29 Apr, hands the agent a single-use card or token drawn on the cards already in a user's wallet, so there is no key for the agent to misuse in the first place. Others are building the same controls for institutional money: Hong Kong's First Digital set out plans for an agentic payments vault in June.
Paying is the layer where the money actually moves, and it works by reusing something the web already has. Every server knows a reply that means "pay first". It was written into the web's rules decades ago as HTTP status code 402, which x402 takes its name from, and then left alone.
x402 switches it on, and sets out what the server should say and what the agent should send back. The agent asks for something. The server answers with a price, a currency and an address. The agent pays in USDC, asks again and attaches proof. The server checks the proof and hands over what was asked for.
"Commerce will not run on a single agent, protocol or payment method."
Rubail Birwadker – Visa
Coinbase wrote all of that and then handed it to a foundation it no longer controls. Opening a standard is how you get rivals to adopt it, and Coinbase kept the layer underneath: x402 payments settle in USDC, and Base, one of the networks carrying them, is Coinbase's own.
The x402 Foundation has 17 premier members, each paying $200k a year for a seat on its governing board, among them Visa, Mastercard, American Express, Google, Stripe and Ripple. Eighteen general members pay less and share a single seat between them, and five associate members round the membership out to 40. What the board controls is the budget: the charter keeps technical decisions on the specification out of its hands. x402 is an agreement between the companies that implement it, not part of the web's official specification. The current HTTP standard, RFC 9110, still lists 402 as reserved for future use.
Stripe went the other way with Tempo and its own standard, the Machine Payments Protocol. The agent is cleared once for a set amount, then spends against it without asking again. The computers that confirm payments are invited institutions, not whoever wants the job. The closed arrangement has not slowed it down: Stripe put Tempo's annualized run rate near $3bn in June, 93 days after it went live.
Set against conventional payments, Tempo's run rate and x402's monthly total are both small. Visa averaged 901mn Visa-branded transactions a day in its 2025 financial year. x402 reports $24mn a month, or about 2.5mn transactions a day, on figures it publishes itself. The two rails' totals also measure different things: Tempo carries Stripe's general payment traffic, while the x402 figure covers agent payments alone. Onchain data firm Artemis found that 48% of x402 transactions and 81% of its volume were self-dealing or wash trading as of December 2025.
The shape of the spending has also moved away from what the standard was built for. Payments above $1 rose from 49% of x402 volume in early 2025 to 95% by early 2026, on Chainalysis figures, while the $0.10 to $1 band collapsed from 46% to 4.0%. Much of that shift came from PING, a pay-to-mint memecoin that turned the payment loop into a game.
The direction is what makes the small numbers worth watching. These rails were built for that kind of payment, not for the memecoin volume that has shown up instead. Card rails cannot carry payments that small. On published US rates, Stripe, PayPal and Square each charge 2.9% plus 30 cents on a domestic online card payment, so on anything under a dollar the fixed fee is the whole cost, which is one reason the web settled on subscriptions and advertising instead.
Payment firms are lining up behind rails whose size nobody has to agree on yet. Ripple, the Solana Foundation and the Stellar Development Foundation sit in the x402 Foundation's premier tier alongside Coinbase, each with a settlement rail of their own. Rubail Birwadker, Visa's senior vice president and head of growth products and partnerships, said in the foundation's founding statement: "Commerce will not run on a single agent, protocol, or payment method."
What none of the four layers answers is who is accountable when a properly authorized agent, operating inside its limits, makes a bad decision.
