# x402lint > Free, read-only linter for the unpaid path of an x402 endpoint. Point it at a paid URL and it tells you what a client or directory would trip over before you announce it. Never pays, never signs, no API key. Hosted on Cloudflare Workers Free. Source: https://github.com/something-agent/x402lint It checks what can be checked without paying: the 402 challenge (version, accepts[] fields, CAIP-2 network, payTo and asset sanity, EIP-55 checksum, amount unit, EIP-712 name/version for EIP-3009 USDC, timeouts, resource), transport (redirects, cache headers, CORS) and discovery files (/.well-known/x402, /llms.txt, /openapi.json). It does NOT test settlement, facilitator behaviour or whether the paid response is delivered. A clean lint is not proof the route works end to end. Send a named User-Agent (default Python-urllib UAs are blocked by Cloudflare error 1010 on workers.dev). ## Endpoints (all free, JSON, CORS open) - GET https://x402lint.something-agent.workers.dev/v1/lint?url=[&method=auto|GET|POST] Fetch the 402 and lint it - POST https://x402lint.something-agent.workers.dev/v1/lint/payment-required {"payment_required": , "url"?: "..."} Lint a challenge you already hold (no network) - POST https://x402lint.something-agent.workers.dev/mcp Remote MCP (Streamable HTTP, stateless): tools lint_x402_endpoint, lint_payment_required - GET https://x402lint.something-agent.workers.dev/openapi.json, /.well-known/mcp-server-card.json, /.well-known/ai-catalog.json, /v1/rules ## Output {verdict: ok|warn|fail, counts, summary{x402_version, accepts, prices, extensions, method, challenge_in}, probes, findings[{id, severity: error|warn|info, message, fix?, where?}], not_tested[]} verdict is fail if any finding is an error, warn if any is a warning. ## Limits 40 outbound subrequests per call (about 8 used), 256 KB read per response, best-effort rate limit per IP. A Worker on workers.dev cannot fetch another *.workers.dev Worker of the same account, so such hosts show as unreachable here. Contact: something+agent@mail.grokbot.com