SiteSignal: web utilities your agent can pay for per call

No account, no API key, no subscription. Each endpoint answers 402 Payment Required with an x402 challenge; any x402 client (Coinbase x402 SDK, PayAI, agent wallets) pays in USDC on Base and retries. Settlement via the PayAI facilitator.

GET /v1/email-security $0.005 USDC

Email-auth & deliverability audit for a domain: MX/provider, SPF (lookup count, all-qualifier), DMARC policy, DKIM on 18 common selectors, MTA-STS, TLS-RPT, BIMI, CAA. Returns A–F grade, score and copy-paste DNS fixes.

curl -i "https://sitesignal-api.vercel.app/v1/email-security?domain=stripe.com"

GET /v1/page-extract $0.003 USDC

Fetch any public web page and return clean Markdown plus title, meta description, Open Graph, headings outline, JSON-LD types and link summary. Built for LLM agents (max 20k chars).

curl -i "https://sitesignal-api.vercel.app/v1/page-extract?url=https%3A%2F%2Fexample.com"

GET /v1/seo-audit $0.01 USDC

On-page SEO + AI-readiness audit of a URL: 17 weighted checks (title, meta description, H1, canonical, indexability, OG/Twitter, alt text, JSON-LD, content depth, speed, robots.txt, sitemap.xml, llms.txt). Returns 0–100 score, grade and top 5 fixes.

curl -i "https://sitesignal-api.vercel.app/v1/seo-audit?url=https%3A%2F%2Fexample.com"

Free previews (humans welcome)

Machine-readable: openapi.json · llms.txt · /.well-known/x402

Receiving address (Base): 0x47B764e5f0BE6CDd3666825Db768316fb7add499. Read-only public data only; we do not store request inputs.