x402 is an open standard for autonomous AI agent payments — fractions of a penny per transaction, settled in stablecoins, no card network required. Stable402.com is the exact-match vocabulary domain for this infrastructure layer.
The problem is structural, not incremental. Card networks were designed for human consumers making deliberate purchases. They carry fixed per-transaction fees and percentage-based pricing that make payments below roughly $1 economically irrational. AI agents don't make deliberate purchases — they make thousands of micropayments to other agents, APIs, and data services in the course of completing a single task.
x402 is the answer Coinbase built. Named after HTTP status code 402 Payment Required, x402 is an open protocol standard that allows any server to charge any client — including an autonomous AI agent — fractions of a penny per request. The agent holds a stablecoin balance. The server presents a payment requirement in the HTTP header. The transaction settles before the response is returned. No intermediary. No fraud dispute window. No card-on-file.
Circle CEO Jeremy Allaire put it directly on his February 25, 2026 earnings call: 'The real opportunity is all of the things that AIs need to consume from each other.' Circle is building Arc — a stablecoin payment blockchain with nanopayment capability. Stripe is building Tempo with Paradigm ($500M raised). The infrastructure race is not speculative; it is being capitalized now.
Stable402.com is the exact-match domain for this protocol layer. It is part of the StableClarity Agentic Finance vocabulary network and is available for acquisition as a standalone domain or as part of the broader portfolio.
x402 — HTTP 402 Payment Required
x402 repurposes the HTTP 402 status code — reserved but never standardized since 1991 — as a machine-readable payment protocol. A server signals a price in the response header; a stablecoin-funded agent client pays before receiving the content. Coinbase incubated the standard and opened it to the industry in 2024.
Nanopayments
Circle's term for sub-cent agentic transactions executed via its Arc blockchain. Where card rails break at small dollar amounts due to fixed interchange fees, stablecoin rails have near-zero marginal cost per transaction. Nanopayments make the economics of agent-to-agent service consumption viable at scale.
Machine-to-Machine Commerce (M2M)
The structural shift from consumer-to-merchant payments to agent-to-agent service purchases. A legal agent billing external agents for research. A data agent charging per query. An execution agent paying for market data per tick. M2M commerce requires programmable money embedded directly in software — not card credentials passed through a POS system.
Stablecoin Settlement Layer
Agentic payments require settlement finality that matches execution speed. USDC and other regulated stablecoins — operating on Circle Arc, Coinbase Base, and similar rails — provide dollar-denominated settlement in seconds with programmable logic. The CLARITY Act (Senate markup, March 2026) is building the regulatory foundation for this layer in the US.
Every domain in this collection was registered against active regulatory or market vocabulary.
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