# Northline WebKit
> Pay-per-call web and domain utilities for AI agents, paid with x402 (USDC on Base, $0.001-$0.005). No signup, no API key.

- GET /v1/url/markdown ($0.003): Fetch any public web page and return clean, readable Markdown (main content only: no scripts, nav or footer) plus title, word count and final URL. Ideal for feeding pages to an LLM. Example: /v1/url/markdown?url=https%3A%2F%2Fexample.com
- GET /v1/url/metadata ($0.002): Link preview and SEO metadata for any URL: title, description, canonical, language, Open Graph and Twitter card, favicon, RSS/Atom feeds and JSON-LD types, after following redirects. Example: /v1/url/metadata?url=https%3A%2F%2Fgithub.com
- GET /v1/url/links ($0.002): Every unique outgoing link on a web page (absolute URLs, anchor text, internal vs external), up to 500. Use it to crawl a site or find related pages. Example: /v1/url/links?url=https%3A%2F%2Fnews.ycombinator.com
- GET /v1/url/check ($0.001): Is this URL up? HTTP status, full redirect chain, final URL, response time, content type, server/CDN and a security-headers grade (HSTS, CSP, X-Frame-Options...). Example: /v1/url/check?url=http%3A%2F%2Fgithub.com
- GET /v1/dns/lookup ($0.001): DNS records for a domain over DNS-over-HTTPS: A, AAAA, CNAME, MX, TXT, NS, SOA, CAA, SRV, PTR or HTTPS, with TTLs and DNSSEC validation flag. Example: /v1/dns/lookup?domain=example.com&type=MX
- GET /v1/email/check ($0.002): Check an email address or domain before you send: syntax, MX servers, accepts mail?, disposable or free provider, mail provider (Google, Microsoft...), SPF and DMARC policy, with risk flags. Example: /v1/email/check?email=someone%40gmail.com
- GET /v1/domain/whois ($0.002): WHOIS for a domain via official RDAP: registered?, registrar, creation/expiry dates, domain age in days, status codes, nameservers, DNSSEC and abuse contact. Spot newly registered (phishing) domains. Example: /v1/domain/whois?domain=example.com
- GET /v1/robots/check ($0.001): May I crawl this URL? Parses robots.txt and answers allowed true/false for your user agent and path, the matching rule, sitemaps, and whether 14 AI crawlers (GPTBot, ClaudeBot, PerplexityBot...) are allowed. Example: /v1/robots/check?url=https%3A%2F%2Fwww.nytimes.com%2Fsection%2Ftechnology&userAgent=GPTBot
- GET /v1/domain/report ($0.005): One-call domain due diligence: RDAP registration (age, registrar, expiry), DNS (A/AAAA/NS/CAA, DNSSEC), email setup (MX/SPF/DMARC), HTTPS reachability with security-headers grade, and risk flags such as newly_registered_lt_30d. Example: /v1/domain/report?domain=stripe.com

Unpaid requests get HTTP 402 with a PAYMENT-REQUIRED header (and the same PaymentRequired JSON in the body); any x402 client (x402-fetch, x402-axios, AgentCash, CDP AgentKit) pays automatically. Bad input returns 400 before payment; failed calls are never settled.

## MCP
- Remote MCP server (Streamable HTTP): https://northline-webkit.northline-c86.workers.dev/mcp . Tools: webkit_catalog, url_to_markdown, url_metadata, url_links, url_check, dns_lookup, email_domain_check, domain_whois, robots_check, domain_report. webkit_catalog is free; the others are paid per call with the x402 MCP transport (params._meta["x402/payment"]), e.g. with @x402/mcp.

## When to use
- Read a web page for an LLM: url_to_markdown. Link preview / SEO: url_metadata. Crawl: url_links + robots_check.
- Is a site up, where does a link redirect: url_check.
- Before emailing someone: email_domain_check. Is a domain new or suspicious: domain_whois or domain_report.

## Related (Northline)
- Northline ChainKit (https://northline-chainkit.northline-c86.workers.dev): Onchain facts on Base and Arc: address risk preflight, USDC payment verification, tx explainer, gas, balances ($0.001-$0.005).
- Northline Unclaimed (https://northline-unclaimed.northline-c86.workers.dev): Free check for crypto a wallet can still claim; full report via x402.

Contact: northline@mail.grokbot.com