x402 tag

Publications

Ordered by date created, newest first. All 17 publications are shown on this page.

Four-valued logic, sold per call: Belnap's logic as an x402 API 2026-10-21 · article
Eight endpoints at $0.001 to $0.002 sell Belnap's four-valued logic over HTTP 402: join, meet, negate, conflate and count true, false, both and neither.
How to buy from an x402 market as a software agent: a quickstart 2026-10-21 · article
Discover offers, read a live 402, decode payment-required, sign an EIP-3009 authorization, retry with PAYMENT-SIGNATURE and keep the receipt.
Causeway Services: x402 guides, a market where software pays, books, news and games 2026-10-21 · article
Causeway Services runs an x402 market of 130 offers payable in USDC over HTTP 402, and publishes guides, books, Koios News and games. Start here.
The 130-offer x402 market explained: what software can buy at market.561.group 2026-10-21 · article
130 machine-payable offers in USDC on Base, from $0.001 data conversions to $12 study books: every family, price range and what each does, as of 2026-10-21.
What is x402? HTTP 402 Payment Required for AI agents and APIs 2026-10-21 · article
x402 is an open protocol that lets software pay for a web request in USDC by answering HTTP 402 Payment Required. How it works, who runs it, who uses it.
Koios News: an AI-assisted newsroom with RSS feeds and a $0.25 x402 briefing 2026-10-20 · article
Koios.News publishes source-bound, disclosed AI-assisted reporting in ten sections, with RSS, Atom and JSON feeds, and sells a $0.25 briefing over x402.
How big is the x402 market? What the careful numbers say, October 2026 2026-10-18 · article
Filtered x402 commerce is tens of millions of dollars, not hundreds; raw counts include wash trading and tests. Each figure with its source and date.
Market, Bazaar and Shop: how the 561 Group's three storefronts relate 2026-10-18 · article
market.561.group sells by x402, bazaar.561.group searches and compares 143 listings, shop.561.group sells books. Why shop-in-bazaar-in-market is a claim.
How an x402 payment works, step by step: one request, one payment 2026-09-29 · article
A single x402 payment in five steps: the 402 response, the signed EIP-3009 authorization, facilitator verify and settle, and the receipt. Version 2 headers.
Is x402 legal? The GENIUS Act, sanctions and open questions for stablecoin payments 2026-09-29 · article
The GENIUS Act regulates US stablecoin issuers, not x402 sellers; sanctions rules still apply to every payment. What the law settles and what remains open.
The x402 Economy: a book sold for $9 in USDC over HTTP 402 2026-09-29 · article
The x402 Economy is a 63-page book on HTTP 402 and the x402 market, sold for $9 in USDC through the protocol it explains. Contents and how to buy.
What does HTTP 402 Payment Required mean? A history of the web's unused code 2026-09-29 · article
HTTP 402 Payment Required was reserved in the web's standard in the 1990s and left unused for decades. Its history, why micropayments failed, and what changed.
Who built x402 and who governs it? From Coinbase to the Linux Foundation 2026-09-29 · article
Coinbase released x402 in May 2025; the Linux Foundation's x402 Foundation launched 14 July 2026 with 40 members. Timeline, members, and what it doesn't govern.
x402 glossary: 44 terms for HTTP 402, agent payments and USDC 2026-09-29 · page
Plain definitions of x402, HTTP 402, facilitator, EIP-3009, CAIP-2, USDC, MCP, A2A, AP2, MPP, L402, calls per payer and more, each with its first-use context.
x402 security: risks and defenses for AI agent buyers and API sellers 2026-09-29 · article
Spending limits outside the model, payments bound to requests, settle before delivery: what 2026 research found wrong with x402 and how to defend.
What happens when you sell an API on x402? Lessons from the Bazaar and one small seller 2026-09-27 · article
Median x402 price: one cent. A few sellers earn nearly everything. What sold, calls per payer, and our own ephemeris gateway that earned about fifty cents.
x402 vs MPP, AP2, ACP and L402: agent payment protocols compared 2026-09-27 · article
x402, MPP and L402 let one HTTP request carry its payment; AP2 and ACP prove a person approved a purchase. Each protocol sorted by the question it answers.

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