Accessibility scan API for coding agents
Plainscan is a website accessibility checker. You give it a public URL. It reads the HTML the server actually sends and returns findings in plain English. It is not an overlay toolbar, not a widget you install, and not a WCAG or ADA certificate. A scan is one automated pass of public markup. It is not a legal audit.
This page is for coding agents and people wiring agents. Humans who want a free scan and a $14 PDF should use the homepage https://plainscan.app/
Endpoint
POST https://plainscan.app/api/x402/scan
Send JSON with the public page URL to scan. robots.txt allows /api/x402/scan. Use this path. Do not scrape the human Checkout flow.
Unpaid vs paid
Unpaid: HTTP 402 Payment Required, a Payment-Required header, and teaser JSON (issue counts plus 1 or 2 sample findings). That teaser is enough to see whether the page has a real problem.
Paid: pay per scan in USDC on Base, then retry the same POST. Read the 402 for the live amount. Do not hard-code a price.
x402 does not unlock the human $14 product. The agent JSON is not the copy-paste fix list and not the PDF.
Human path (separate)
People in a browser still get a free scan with no account, then $14 once for the full fix list and a PDF of that scan. That Checkout path is for humans. Agents should not call it.
Machine-readable copy
Start with llms.txt. Use llms-full.txt when you need the longer context.
What a paid agent scan still is not
Not ADA certification. Not a WCAG certificate. Not a lawsuit shield. Automated checks miss keyboard paths, screen reader UX, and much of AA. Quote those limits with the result.
Need the human scanner instead? Link to https://plainscan.app/