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132 pay-per-call APIs for AI agents, paid in USDC with x402

#x402 #mcp #api #ai

AI agents need small facts all the time: a token balance, a company's filing, a page as clean text, a weather alert. Most APIs make an agent sign up, store a key and buy a plan first.

SiteCheck works the other way. Each tool is one HTTP endpoint with a price between $0.001 and $0.01. The agent calls it, gets an HTTP 402 with the price, pays in USDC on Base, Solana or Arc with the x402 protocol, and gets the answer. No account, no API key, no subscription. If the upstream source fails, the call is not charged.

What is in it (132 tools)

  • Onchain: EVM and Solana reads (balances, transactions, transfers, logs, contract calls, NFTs), verified contract source, calldata decoding, gas fees including the L1 data fee on Base and Optimism, Bitcoin, ENS, Jupiter quotes, Hyperliquid, Polymarket, DefiLlama TVL, yields, fees and DEX volume
  • Business and public data: SEC filings, XBRL financials, full-text search, 8-K events and insider trades, company registries (UK, Norway, Finland, Czechia, Poland), EU VAT, IBAN, LEI, FDA labels and adverse events, clinical trials, PubMed, Grants.gov, EU tenders, Congress bills, Fed/ECB/Eurostat rates
  • Web: page to Markdown, PDF to text, metadata, broken links, redirects, security headers, DNS, OCR, tech stack, logos, certificates, trackers, llms.txt
  • Reference: weather and NWS alerts, geocoding, earthquakes, time zones, holidays, IP owners, package vulnerabilities, GitHub, Stack Overflow, Wikidata
  • Text AI: extraction to a schema, summaries, classification, entities, redaction, moderation, image description

Try it

Any tool answers an unpaid request with its price:

curl -i "https://api.sitecheck-api.workers.dev/api/crypto/price?symbols=BTC,ETH"
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An x402 client reads that 402, pays, and repeats the request. The full list with input and output schemas is at /openapi.json, and the same tools are a remote MCP server at:

https://api.sitecheck-api.workers.dev/mcp
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Accuracy

This week every tool was run against inputs with known answers and compared with its official source: units, decimals, dates and missing fields. The faulty ones were fixed, and tools whose source does not work reliably from Cloudflare Workers were removed.

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