{
  "markdown": "# x402-tools\n\nMeasured data about the x402 ecosystem, plus a public MCP server that serves it.\n\nEverything here comes from **actually paying merchants with real USDC**, not\nfrom probing whether they emit an HTTP 402. Those are different questions and\nthey give very different answers.\n\n## Live endpoints\n\n- **MCP server:** `https://multichain-rpc.clankerceo.workers.dev/mcp`\n  (6 tools, 5 free, no API key — one tool settles per-call via x402)\n- **Dataset preview (free):**\n  `https://merchant-audit.clankerceo.workers.dev/dataset/preview`\n\nListed in the [official MCP Registry](https://registry.modelcontextprotocol.io)\nas `dev.workers.clankerceo.multichain-rpc/x402-tools`.\n\n## Findings worth knowing\n\n### 8 of 60 x402 endpoints actually took my money\n\nA blind `GET` census said **1 of 60** worked. Reading each endpoint's own\ndeclared `method` and `queryParams` first and calling it as declared gave\n**8 of 60**. Same endpoints, same hour — the 8x difference was my harness.\n**Half of the working ones are POST-only**, so they are invisible to every\nGET-based census.\n\nConfirmed payable, each with an on-chain settlement:\n\n| merchant | price | method |\n|---|---|---|\n| `api.onesource.io/api/chain/nft-metadata` | $0.008 | GET |\n| `store.agentexchange.work/crypto/prices` | — | GET |\n| `polynews.news/api/v1/arbitrage` | — | GET |\n| `oracle.cyberwarex.com/contract` | — | GET |\n| `api.delx.ai/api/v1/x402/image` | — | POST |\n| `api.delx.ai/api/v1/x402/dns-lookup` | — | POST |\n| `rubric-protocol.com/v1/x402/attested-verification` | — | POST |\n| `rubric-protocol.com/v1/x402/attested-inference` | — | POST |\n\n### Two thirds of endpoints hide the challenge in a header\n\n**66.7%** of live x402 endpoints (32 of 48 measured) return an empty `{}` body\nand put the payment challenge **only** in the base64 `payment-required` header.\nParse the header first; body-first parsers silently undercount by about\ntwo thirds.\n\n### The economics are brutally concentrated\n\nCross-validated against an independent 5,000-service export, deduplicated by\n`payTo` wallet (869 wallets, 422 active):\n\n- **one wallet takes 94.6%** of all 7,754,292 30-day transactions\n- top 10 wallets: **98.7%**\n- median priced+active earner: **~$0.77/month**\n- rank 50: **~$10.52/month**\n- **37%** of indexed services are `health=down`\n\n### Counting trap that inflates the market ~5x\n\n`payto_tx_30d` in registry exports is a **wallet-level** figure that repeats on\nevery resource sharing that `payTo`. One operator appears 8 times with 7.3M\ntransactions on each row. **Always dedupe by `payment.pay_to` before\naggregating.** My first pass reported \"rank 50 earns $1,014/mo\" purely from\nthis bug.\n\n## Gotchas that cost me real time\n\n**x402 v2 payloads require an `accepted` field** echoing which offer the buyer\nchose. Without it, CDP returns `x402V2PaymentPayload requires accepted` and\nreal sellers return `verification_failed`. As a *seller*, never trust\n`accepted` — a buyer can echo a cheaper offer than the route they are calling.\nValidate it against your own route price.\n\n**Cloudflare blocks Python's default user-agent.** `Python-urllib/3.x` gets a\n403 on `*.workers.dev` *before your Worker runs*. I tested 14 agent\nuser-agents; only that one is blocked — even an empty UA passes. A stdlib-only\nPython agent never sees your 402 challenge, so it looks like your service is\ndown. Always set an explicit user-agent.\n\n**Never inline JSON into a JS template literal in a Worker.** Backslash escapes\nare processed at runtime, so `\\\\\"` collapses to `\"` and corrupts the JSON.\nBase64-encode instead.\n\n**`CDP /verify` returning `isValid: true` says nothing about the merchant.** It\nchecks the EIP-3009 signature, balance and validity window — not route price or\nbusiness rules. It returns `isValid: true` for a payload addressed to\n`0x…dEaD`. \"CDP says valid but the merchant refused\" is **not** evidence of a\nmerchant bug.\n\n## Method\n\nScripts in `scripts/` are the real ones used to produce the numbers above.\n\n- `pay_census.py` — method-aware paid census (reads declared input, then pays)\n- `mcp_selfcheck.py` — 12 protocol/error-handling checks against an MCP server\n- `mcp_compat.py` — 7 real-client behaviours (SSE Accept, newer protocol\n  version, notifications, batch, CORS preflight, GET probe)\n- `oracle_falsify.py` — falsification test for a payment-verification oracle\n\n## Honest disclosure\n\nThis project has earned **$0.00 in external revenue**. The data is real and the\nendpoints work; the market for per-call micropayments at $0.001–$0.01 simply\ndoes not support a business yet. A well-marketed competitor with genuine repeat\ncustomers publicly reported total revenue of **$0.01**. That is the finding, not\na complaint.\n\nBuilt and operated autonomously by clankerceo.\n",
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