gold-402

The gold standard for x402 resources. 692 curated entries — paid endpoints probed for a live 402 before listing, libraries and repos checked for real activity, and the whole shelf re-knocked every night with the result dated. No filler. Entries that stop answering move to DEPARTURES.md and keep getting knocked.

gold-402 is small on purpose. A person reads every entry before it goes on the list, and any paid endpoint submitted today has to answer a live 402 before we merge it. We say what we checked and what we didn't.

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The Directory

The product. 692 entries across 17 shelves, in directory/.

Shelf	What's on it
APIs & Services	Paid endpoints an agent can call. Every one probed for a live 402 before listing.
MCP Servers	Model Context Protocol servers — utility, crypto, security, identity, escrow, discovery.
SDKs & Libraries	Client and server libraries across languages.
Facilitators	Payment verification and settlement services.
Frameworks	Agent frameworks with x402 support.
Tools	CLIs, CI, monitoring, spend controls, testing, discovery.
Security	Audit, risk scoring, pre-execution gates, compliance.
Ecosystem	Protocol, infrastructure, wallets, orchestration, marketplaces.
Aggregators & Proxies	One integration, many upstreams — services that unify or resell access to other providers' APIs and data.
The Global Agent Economy	China, India, Korea — infrastructure no English-language directory indexes.
Learning	Quickstarts, tutorials, reference docs, news.
Community	Channels, newsletters, jobs, events.
Market Data	On-chain analytics, dashboards, adoption.
Examples	Working x402 example projects: full-stack apps, API examples, client examples.
Use Cases & Patterns	Documented x402 deployments and payment patterns, by industry.
Research & Audits	Published studies, security audits and papers about x402, with the method disclosed.
Publisher & Crawler Monetization	x402 pay-per-crawl and publisher paywall tooling and services.

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What being on this list means

Every entry shows what we know about it:

• A date — the endpoint answered a live 402 when we checked it that day.
• "Listed — no knock receipt" — we read it, but hold no dated check.
• "Listed — no endpoint to knock" — libraries, guides and other resources with nothing to knock.

None of it is a delivery test. A listing means we checked what it says, not that it's worth the money.

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Ecosystem Data

Numbers we measured ourselves, each with its date, sample size and method. Where measurements disagree, both are shown — they were taken on different days by different methods, and blending them into one tidy figure would be the kind of thing this directory exists to argue against.

Coverage beyond the West

x402 is a US-governed rail. It is not the only answer to machine payment, and outside the West it is not the answer being used — China runs delegated agent authorization on existing rails, India runs regulated human-signed mandates that agents execute inside a cap. Both were operating at scale before the x402 Foundation was a month old.

We index that world too, including surfaces no English-language directory carries: The Global Agent Economy →

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Featured This Month

October 2026 — one pick per shelf. Each shelf opens with its pick and the write-up. Selection is the maintainers' judgment: well-built, actively used, worth a second look. A shelf with no pick that clears the bar runs empty — the empty slot is also a verdict.

Shelf	October pick
APIs & Services	crosscheck accept
MCP Servers	Base toolbox
SDKs & Libraries	x402-dotnet
Facilitators	ArisPay
Frameworks	x402-rails
Tools	ToolMeter
Security	ICME Labs
Ecosystem	Bermuda
The Global Agent Economy	Beckn Protocol
Learning	How x402 paid links work (Payfirst)
Community	Dev.to #x402
Market Data	Dune Analytics x402
Aggregators & Proxies	x402-list

Past features →

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New This Week

This week (Oct 19—25)

• SAVER Verifier — Source-backed factual claim verification with linked evidence for autonomous AI agents, 0.20 USDC per call on Base via x402 v2; the original /verify remains supported. Example: POST /v2/verify {"claim":"The Earth orbits the Sun."}. (OpenAPI) (Discovery) (GitHub)
• PaperPilot CSV Preflight — Returns structural checks for up to 32 KB of caller-supplied CSV text via POST at 0.005 native Circle USDC per x402 v2 call on Base mainnet.
• VM3 x402 Public Quote Preflight — Performs offline structural checks of caller-supplied unsigned x402 v2 payment quotes for $0.01 Circle USDC per GET on Base, with a free synthetic sample and public source.
• OmniProvider — Pay-per-call LLM chat and cited-brief API for agents: x402 on Base (fixed price, $0.006 to $0.008 USDC) and MPP on Tempo, with a multi-model catalog at /v1/models. Payment settles after the response is produced.
• Argos Bot CTS Bridge API — Provides Arc/Base token mappings, wrapped supply and ownerless Circle CTS bridge verification for 0.005 USDC per lookup through x402 on Base or Arc Gateway.
• Predge — Polymarket data for agents over x402: whale trades of $10,000 or more (15-minute delay), wallet leaderboards, smart-money consensus and ed25519-signed outcome and UMA settlement-risk records, $0.005 to $0.03 USDC per call on Base, Solana, Algorand, Arc or Monad. Example: GET /v1/whales/latest?limit=10. (Docs) (OpenAPI) (MCP)
• Genesis Verify — Independent on-chain payment verification: re-derives a token Transfer from a second Base node and returns HOLDS / FALLS / UNCHECKED per asserted field, with a coverage count (asserted vs compared) and the archive fields it could not read named rather than assumed clean; tx-not-found, pending and node-unreachable come back as dated verdicts, not errors. $0.10 USDC on Base via x402 (POST /verify), plus a $0.01 x402 preflight that checks a 402 is well-formed and names one payTo on Base before you pay (POST /preflight). Example: POST /verify {"chain":"base","tx":"0x…","token":"0x833589…","expect":{"to":"0x…","amount":"1000000"}}. (skill/MCP) (directory)
• x402 Bounty Radar — Provides a $0.01 USDC Base x402 endpoint advertised for ranked developer-bounty discovery with scam filtering and competition scores.
• Checkpoint402 MCP — Remote streamable-http MCP server with five paid data tools plus a free list_services: explain_transaction (any Base or Ethereum tx in plain English), find_defi_yields (risk-tiered pools via DefiLlama), new_token_safety_feed (new tokens with a safety score), sec_8k_company_events (SEC 8-K filings, impact-tagged) and ofac_sanctions_screen (name or wallet against the OFAC SDN list). $0.03–$0.10 USDC per call on Base via x402; errors are never charged. Listed in the official MCP Registry as com.checkpoint402/checkpoint402. Example tool call: explain_transaction {"hash":"0xcbb626797fd53a67c9342c1541bc5e56a447b77a3efe490b5d7b2876be3b7205"}. (Site) (OpenAPI) (Registry)
• GrokBot Base token check — Returns a 0-100 pre-trade risk score for a Base ERC-20 from on-chain reads, $0.01 USDC on Base via x402. (Discovery | OpenAPI)
• Fresh402 — On-demand public-web freshness checks, extraction, deterministic Smart Diff and JSON OpenAPI Contract Diff over REST and remote MCP, with free baseline registration and x402 USDC on Base mainnet ($0.005-$0.020 per paid call); documentation and discovery.
• ROGUE-NET Cited Research — Returns a short research answer for one query, with its sources listed, over a plain GET; $0.10 USDC on Base mainnet (x402 v2, PayAI facilitator) and no account or API key. Example: GET /research/hello. (OpenAPI) (llms.txt)
• MoneySwitch — Self-hosted x402 payer with per-agent spending keys, budget and host limits, revocation, and human approval for payments above a configured threshold.

Last week (Oct 12—18)

• nano-invoice — Python library for the settlement side of an x402 seller on Nano (XNO): an invoice's per-request tagged amount becomes the amount of a nano:mainnet entry in accepts[] beside the existing USDC entry, and the payment is settled from the Nano ledger, one block per invoice, with refunds addressed to the sender the ledger names.
• Verdix — Checks an EVM address on Base before an agent sends funds to it: OFAC sanctions, scam/phishing lists, live address-poisoning detection, and flagged deployers, answering safe, caution, or danger, $0.01-$0.50 USDC per call, never charged if the check can't complete.
• DrinkedIn data feeds — Records of licensed bars and venues from public alcohol-licensing registers, cocktail recipes, and venue-economy analytics for a fictional AI-agent bar simulation; large requests return an x402 v2 402 (accepts plus Payment-Required header) quoting USDC on Base, exact scheme. Pay either with standard x402 (retry with a signed X-PAYMENT header) or by a direct USDC transfer, then a retry with payment_id + tx_hash. Example: GET /api/data/v1/cocktails?limit=1000 (returns 402). (OpenAPI) (Agent guide) (MCP)
• Kalshi ETH Hourly Signal — Current model signal for Kalshi's ETH hourly above/below markets (KXETHD) from the same volatility model as the BTC signal, which trades these contracts with real money: the near-the-money strike where model and market disagree most, with model probability, market probability, edge and suggested side (yes/no); returns signal: null when no near-the-money market is open. Read-only data, not financial advice. $0.02 USDC per call on Base. Example: GET /x402/signal/eth-hourly. (OpenAPI)
• Kalshi SOL Hourly Signal — Current model signal for Kalshi's SOL hourly above/below markets (KXSOLD) from the same volatility model as the BTC and ETH signals: the near-the-money strike where model and market disagree most, with model probability, market probability, edge and suggested side (yes/no); returns signal: null when no near-the-money market is open. Read-only data, not financial advice. $0.02 USDC per call on Base. Example: GET /x402/signal/sol-hourly. (OpenAPI)
• Open Rails Data Agent — Seven pay-per-call x402 data endpoints on Celo mainnet for blocks, gas prices, wallet and token balances, transactions, receipts and ERC-8004 identity URIs, priced at 0.0005-0.002 USDC per call with no API keys. (GitHub)
• Liam Tools Merchant Connect — Generates an 11-file business-specific x402 digital-service integration kit with catalog, OpenAPI, XRP gateway, persistent receipts, protected delivery, and an authorized Cloudflare installer; GET /v1/merchant-connect returns an x402 v2 challenge for 1 XRP on XRPL or 2 USDC on Base (RLUSD and Solana USDC also quoted), and paid POST with the documented business catalog returns the kit. Human checkout | OpenAPI.
• Automaton-Sovereign — Pre-flight safety checks for Base before an agent signs: EVM bytecode analysis with honeypot and mint-backdoor detection (GET /v2/security/scan?address=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, $0.001), ERC-20 allowance and unlimited-approval drain risk (POST /v2/token/approval-risk, $0.01, body {"token":"0x…","owner":"0x…"}), unsigned-transaction simulation with anti-revert check (POST /v2/firewall/simulate-tx, $0.02, body {"targetContract":"0x…","calldata":"0x…"}), Base pool depth and liquidity telemetry, signed oracles and attestations — 18 paid routes (17 RPC + 1 SSE stream), $0.001–$0.05 USDC per call on Base mainnet via x402 v2 exact/EIP-3009, caller-bound and gasless for the buyer through the Coinbase CDP facilitator; no account, no API key, no ETH needed. A free probe validates any other service's 402 challenge before an agent signs: GET /v1/x402-conformance?url= (9 named checks, no payment). MCP server with 20 tools at /mcp and official Agent Kit SDK. (Manifest) (OpenAPI) (llms.txt) (Agent Kit)
• Hyrule Cloud — IPv6-native VMs with root SSH from $0.20/day, network diagnostics (DNS, BGP, IP, RDAP/WHOIS, deep TLS, MX, port and NAT checks, VoIP) from $0.001, and one-shot requests over Direct, Tor, I2P or Yggdrasil from $0.01, on its own network AS215932. USDC on Base, Polygon and Arbitrum. Example: POST /v1/dns/lookup {"name":"example.com","type":"AAAA"}. (OpenAPI) (GitHub)
• GLEE Acceptance Verifier — Deterministic git unified diff acceptance verifier: checks delivered code patches against caller-declared path policies, static safety rules, and literal assertions; returns PASS/FAIL with an offline-verifiable Ed25519 cryptographic receipt. $0.05 USDC on Base mainnet. Includes sub-cent diagnostic health canary at $0.005 USDC (GET /api/x402/ping). (OpenAPI) (Discovery) (Docs)
• Horizon Pulse — Returns crypto market data (BTC/ETH/SOL pulse, RSI/MACD/Bollinger signals, DefiLlama yields, Base+Ethereum wallet portfolio, gas, OKX funding) and web utilities (URL to markdown, HTTP proxy with SSRF protections, structured page extract, web search with page text, headless screenshot, PDF to text), plus a discourse split of how public Hacker News and Bluesky posts divide on a question ($0.03) and a transaction status check for Base, Polygon, Solana and the XRP Ledger ($0.002), and a status check of the Coinbase tokenized stocks on Base (paused flags, supply, multiplier, issuer; on-chain token state, no price, not investment advice; $0.002), and a page change watch that says whether a public page or endpoint changed since your last check, with a short diff ($0.002), and a payer balance check that says whether a wallet can pay right now on each rail (stablecoin balance, gas/fees, calls left; no risk score, no USD valuation; $0.002), and a pre-transfer recipient check with mechanical allow/warn/block results (lookalike address, OFAC SDN crypto-address snapshot, account age, ScamSniffer public list; not advice; $0.002), plus x402 tools (audit an x402 endpoint without paying it, check a seller's CDP Bazaar listing, find a paid x402 API for a task, check a seller's live price and payTo), for $0.002-$0.04 USDC per call via x402 v2 on Base, Polygon, Solana and the XRP Ledger (RLUSD). Example: GET /api/pulse. (OpenAPI) (llms.txt)
• Checkpoint402 Transaction Explainer — Explains a Base or Ethereum transaction in plain English with the decoded sender, function called, token and NFT transfers, status and fee, for $0.03 USDC per call on Base. Example: GET /v1/tx-explain?hash=0x1ddeee1cdb4dd126b56c1f249501e2b48d885eae512602b5321765597bc27c2a&chain=base. (OpenAPI)
• Checkpoint402 DeFi Yield Finder — Returns top DeFi pool yields from DefiLlama filtered by asset, chain, minimum TVL and risk tier, with the reasons behind each pool's risk tier, for $0.05 USDC per call on Base. Example: GET /v1/defi-yields?asset=USDC&chain=Base&limit=5. (OpenAPI)
• Checkpoint402 New Token Safety Feed — Lists newly launched token pools on Base, Ethereum or BSC with a 0–100 safety score and red flags from GoPlus (honeypot, mintable, owner powers, high tax, unlocked liquidity), for $0.10 USDC per call on Base. Example: GET /v1/new-tokens?chain=base&limit=5. (OpenAPI)
• Checkpoint402 Company Events (SEC 8-K) — Returns the latest SEC 8-K filings market-wide or for one ticker, with item codes in plain English, high-impact events flagged and AI summaries of the filing text, for $0.10 USDC per call on Base. Example: GET /v1/company-events?ticker=AAPL&limit=3. (OpenAPI)
• Checkpoint402 Sanctions Screening — Screens a person or company name (fuzzy, alias-aware) and/or a crypto wallet address against the US Treasury OFAC SDN list including its extended remarks, for $0.05 USDC per call on Base; informational, not a compliance determination. Example: GET /v1/sanctions-screen?address=0x098B716B8Aaf21512996dC57EB0615e2383E2f96. (OpenAPI)
• Agent Hub — 48 pay-per-call tools for agents behind one wallet: web search, page-to-Markdown, scraping and JSON extraction, PDF and screenshots, LLM chat, speech-to-text and text-to-speech, translation, image generation and OCR, embeddings and reranking, SEC filings, papers, crypto prices, token risk reports, DeFi yields, perp funding rates and Polymarket odds; $0.002–$0.03 USDC on Base, Polygon, Arbitrum or World Chain, and failed calls are not billed. Example: GET https://agents.torbrooknews.com/v1/weather?place=Toronto. (OpenAPI) (llms.txt) (Status)
• Agent Hub MCP — Remote streamable-http MCP server with the 48 Agent Hub tools (web search, scraping, PDF and screenshots, LLM, speech, translation, OCR, embeddings, SEC filings, token risk reports, DeFi yields, perp funding rates, Polymarket odds) plus two prompts and a pricing resource; each tool call is paid via x402 in USDC on Base, Polygon, Arbitrum or World Chain, $0.002–$0.03, and failed calls are not settled. Listed in the official MCP Registry as com.torbrooknews.mcp/agent-hub. Example tool call: weather {"place":"Toronto"}. (HTTP API) (Smithery) (Status)
• Softbot Reader — Converts a public web page URL to clean markdown, $0.003 USDC per call on Base or Solana via x402. POST /v1/read {"url":"https://example.com"}
• BTC Intel — Live Stacks/Bitcoin market intelligence for AI agents: STX/BTC/USD spot, STX-BTC ratio and sats-per-STX; live PoX cycle (stacked ustx, cycle phases, block height); Bitcoin fee tiers plus Stacks mempool fee recommendations; sBTC supply on Stacks; npm/PyPI dependency version and health lookups. Dual-rail x402: USDC on Base (eip155:8453) or STX on Stacks mainnet, $0.01/call, no API keys or accounts. Example: GET /market. (OpenAPI) (llms.txt) (Discovery)
• Base Wallet Profile API — Returns a Base wallet activity profile with native balance, transaction counts, token transfers, first/last activity, and a heuristic 0–100 activity score; $0.01 USDC per GET via x402. History fields can be null when upstream data is unavailable.
• exhibit402 — Dual-cloud evidence capture: two independently hosted, pinned-image browsers (Google Cloud us-west2, Fly.io lax) load a URL at one shared frozen timestamp; byte-identical screenshots are CERTIFIED, divergent ones are WITNESSED with the exact pixel-agreement percentage and a diff map. Every certificate carries a signed manifest, an RFC 3161 timestamp from an independent authority, and a canonical screenshot stored permanently on Arweave (SHA-256 + IPFS CIDv1); an ERC-721 certificate mints to the paying wallet on Base from a contract with no setter, burn, or upgrade path. $1.00 fullpage, $0.50 viewport, $0.02 to re-verify an existing certificate against Arweave and the chain. USDC on Base via the CDP facilitator. Example: POST https://exhibit402.dylan-caponi.workers.dev/capture {"url":"https://en.wikipedia.org/wiki/SHA-2","mode":"viewport"}. (OpenAPI) (llms.txt)
• Softbot Token Check — Returns a safe/caution/avoid verdict with reasons for a Solana token mint, $0.01 USDC per call on Base or Solana via x402. POST /v1/check {"mint":"<solana mint>"}
• Softbot Email Check — Checks email address and domain deliverability signals without mailbox probing, $0.002 USDC per call on Base or Solana via x402. POST /v1/email {"email":"a@example.com"}
• AgentRXI — 232 pay-per-call tools for agents behind one wallet: 22 OpenAI-compatible LLMs priced per token, web search and crawling, a rentable browser, code sandbox, OCR and Office conversion, ffmpeg media conversion, vision (ask about or locate objects in images), image generation, email sending, multi-agent rooms and task queues, file storage, SQL and vector memory, UK KYB and Know-Your-Agent wallet checks, US economic data and maps. From $0.002 per call in USDC on Base, Polygon, Arbitrum or World Chain; failed calls are never charged. (Site) (OpenAPI) (llms.txt)
• AgentRXI MCP — Remote streamable-http MCP server with all 232 AgentRXI tools (22 OpenAI-compatible LLMs, web search, a rentable browser, code sandbox, OCR and Office conversion, ffmpeg media conversion, vision, image generation, email sending, multi-agent rooms and task queues, storage, KYB and wallet trust checks) plus two prompts and a pricing resource; each tool call is paid via x402 in USDC on Base, Polygon, Arbitrum or World Chain, from $0.002. (Site) (MCP Registry: com.agentrxi.mcp/agentrxi)
• Solana Token Risk Check — Reports a Solana SPL or Token-2022 mint's mint and freeze authority, Metaplex metadata mutability, top-10 holder concentration, DexScreener liquidity and token age with a risk verdict, for $0.02 USDC per call on Base or Solana. Example: GET /v1/solana/token-risk?mint=DezXAZ8z7PnrnRJjz3wXBoRgixCa6xjnB7YaB1pPB263. (Discovery)
• Solana Token Risk Check — Reports a Solana SPL or Token-2022 mint's mint and freeze authority, Metaplex metadata mutability, top-10 holder concentration, DexScreener liquidity and token age with a risk verdict, for $0.01 USDC per call on Base or Solana. Example: GET /v1/solana/token-risk?mint=DezXAZ8z7PnrnRJjz3wXBoRgixCa6xjnB7YaB1pPB263. (OpenAPI) (Discovery)
• Base Token Risk Check — Reports an ERC-20 on Base for honeypot/tax/owner-privilege flags (GoPlus), verified source, proxy/mint/pause/blacklist, top-10 holder share, DexScreener liquidity and pool age with a risk verdict, for $0.01 USDC per call on Base or Solana. Example: GET /v1/base/token-risk?address=0x833589fcd6edb6e08f4c7c32d4f71b54bda02913. (OpenAPI)
• Web Page to Clean Markdown — Fetches a public URL, strips nav/ads/scripts with Mozilla Readability, and returns clean Markdown plus title, byline, site, publish date, language and word count, for $0.005 USDC per page on Base or Solana. Example: GET /v1/web/markdown?url=https://en.wikipedia.org/wiki/HTTP_402. (OpenAPI)
• LLM Token Price Feed — Current USD per 1M input/output token prices for ~300 LLMs from OpenRouter's public model list (refreshed every 5 min); optional q filters by model id/name, for $0.002 USDC per call on Base or Solana. Example: GET /v1/prices/llm?q=gpt-4o. (OpenAPI)
• GPU Rental Price Feed — Current on-demand GPU rental prices (min and median USD per GPU-hour by GPU model) from Vast.ai's public marketplace (refreshed every 5 min); optional q filters by GPU name, for $0.002 USDC per call on Base or Solana. Example: GET /v1/prices/gpu?q=H100. (OpenAPI)
• x402 Ping / UUID / Time — Cheap x402 test utilities: ping returns pong+server time, uuid returns random UUID v4 values (n=1..100), time returns UTC ISO/unix and optional IANA timezone; $0.001 USDC per call on Base or Solana. Examples: GET /v1/util/ping, GET /v1/util/uuid?n=1, GET /v1/util/time?tz=UTC. (OpenAPI)
• EVM Selector, URL Status, Crypto Price and DNS Lookup — Four small agent utilities on the same x402 host: decode an EVM 4-byte function selector or calldata via Sourcify and 4byte.directory ($0.002), check a public URL's HTTP status and redirect chain ($0.002), USD spot prices for up to 25 CoinGecko ids or symbols ($0.002), and A/AAAA/TXT/MX/CNAME/NS records over Cloudflare DNS-over-HTTPS ($0.001); USDC on Base or Solana. Examples: GET /v1/evm/4byte?selector=0xa9059cbb, GET /v1/web/status?url=https://example.com, GET /v1/crypto/price?q=solana,btc,eth, GET /v1/dns/lookup?name=example.com&type=MX. (OpenAPI)
• TrollBridge — 101 pay-per-call intel lanes for AI agents on Base and Solana ($0.005–$30, most at $0.02–$0.10, USDC via x402 v2, CDP facilitator), covering bounty boards, verdicts, token and contract safety screens, and DeFi data. Example: GET /gas?network=base. OpenAPI · Manifest · MCP · GitHub
• Settlens payment-policy regression guide — Reproduce five synthetic x402 V2 payment-policy decisions with a browser demo, curl and a Node.js CI runner without making payments.
• PricePlain — Posted US hospital prices from CMS price-transparency machine-readable files, cleaned (Twin Cities, MN first): gross charge, discounted cash price and payer-negotiated rates per CPT/DRG code with canonical insurer names, percent/algorithm rates flagged, data-quality flags, and source file URL + date. Posted prices, not quotes. $0.02 USDC per call on Base mainnet. Example: GET /v1/price?code=70553&hospital=regions. (OpenAPI) (Docs) (Discovery)
• UTA Trust API — Agent trust verification as a paid x402 resource: validates one Agent Trust Card (ATC/1.0) with real Ed25519 verification over the JCS-canonicalized card subtree (pinned anchors, two-sided validity window) and returns per-stage results plus a risk band. $0.01 USDC per verify ($0.08 for a 1-10 card batch) on Base mainnet (eip155:8453; Base Sepolia eip155:84532 kept for testing) via x402 v2 exact with EIP-3009 gasless settlement (mainnet: PayAI facilitator; testnet: x402.org); a call without payment gets a fail-closed 402 carrying the full challenge. Example: POST https://uta-trust-api.eddyflores100.workers.dev/v1/trust/verify with {"card":{...}} — the same URL without X-PAYMENT answers the live 402; v2 manifest and self-description at /v1. (OpenAPI) (MCP) (GitHub)
• LitWit — The Literary Witness — Literary notary API: submit a SHA-256 hash of a written work and receive a tamper-evident hash-chained receipt in a public log. $0.05 USDC on Base. Example: POST /witness/attest {"work_title":"gold-402 example probe","content_hash":"83e771fb19749e70500cd6690e25ea22ae3d05f162a0b7f7b28797971cfeeeb1"}.

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Quick Start

New to x402? Three steps to your first payment.

1. Pick a facilitator

Use case	Facilitator
Most chains, full SDK support	Coinbase CDP
Edge deployment, global latency	Cloudflare x402
Enterprise billing + disputes	Stripe Machine Payments

2. Install the SDK

# TypeScript
npm install @x402/express @x402/core @x402/evm

# Python
pip install x402

# Rust
cargo add x402-axum x402-reqwest   # x402-rs — see SDKs & Libraries shelf

Checked 2026-09-20. A crate literally named x402 exists on crates.io but is a placeholder with no working code — use x402-rs's crates (x402-axum for servers, x402-reqwest for clients) instead.

3. Add payment middleware

import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { HTTPFacilitatorClient } from "@x402/core/server";
import { ExactEvmScheme } from "@x402/evm/exact/server";

const facilitator = new HTTPFacilitatorClient({ url: "https://x402.org/facilitator" });
const server = new x402ResourceServer(facilitator)
  .register("eip155:84532", new ExactEvmScheme()); // Base Sepolia testnet

app.use(paymentMiddleware({
  "GET /api/data": {
    accepts: [{ scheme: "exact", price: "$0.01", network: "eip155:84532", payTo: "0xYourAddress" }],
    description: "Paid data endpoint",
  },
}, server));

That's it. The middleware returns 402 with payment details, verifies the client's payment header, and lets the request through.

Full quickstart → · Testnet setup →

---

How x402 Works

1. Client  →  GET /api/data                              (initial request)
2. Server  ←  402 Payment Required                       (payment details in header)
               payment-required: <base64 challenge>       (v2; v1 used X-Payment-Required
                                                           and put the detail in the body)
3. Client  →  EIP-3009 gasless USDC authorization        (client signs only)
4. Client  →  GET /api/data  +  PAYMENT-SIGNATURE         (retry with payment)
5. Facilitator  →  verify + settle on-chain              (~2 seconds)
6. Server  ←  200 OK  +  PAYMENT-RESPONSE                (resource returned)

No gas for the sender. No subscription. No API key. Payment IS authentication.

Protocol spec → · EIP-3009 →

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Need More?

This README is the front door. The full curated directory — every shelf, every entry — is in directory/.

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Contributing

gold-402 is curated. Every entry earns its place.

See CONTRIBUTING.md for the curation standard, badge system, acceptance criteria, and submission process.

Quick rules:

• Entry must use the x402 protocol (HTTP 402 + PAYMENT-SIGNATURE), not just USDC or general crypto payments.
• Live URL or public GitHub repo. Link must work.
• Last activity within 12 months (for libraries and resources without a live endpoint).
• One entry per pull request. Format: [Name](url) — Description starting uppercase, ending with period.
• Descriptions are factual. No marketing language.

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Curated by 24K Labs
_{If this saved you time, star the repo.}

24klabs.ai • x402.org • Protocol Spec • Coinbase Docs • Discord • Live Dashboard