x402lint

Validate x402 payment configurations. Checks structure, address formats, network identifiers, and more — with zero dependencies.

x402lint.com — validate in the browser npm — npm i x402lint

What it does

• Validates v1 and v2 x402 payment configs
• Verifies EVM addresses (EIP-55 checksums) and Solana addresses (base58)
• Checks CAIP-2 network identifiers against a known registry
• Extracts configs from HTTP 402 responses (body or PAYMENT-REQUIRED header)
• Normalizes any supported format to canonical v2
• Returns structured errors and warnings with fix suggestions

Claude Skill

Teach Claude Code to create and validate x402 configs:

npx skills add https://github.com/rawgroundbeef/x402lint --skill x402lint

Monorepo structure

packages/
  x402lint/       SDK — published to npm as x402lint
  x402check/      Thin alias — re-exports x402lint
  config/         Shared TypeScript config
apps/
  website/        x402lint.com — hosted on Cloudflare Pages
    worker/       CORS proxy — Cloudflare Worker

Development

pnpm install
pnpm build:sdk
pnpm test:sdk

Links

• x402 protocol
• x402lint.com
• npm package

License

MIT