# Services from email-preflight-api.vercel.app on Zero

> email-preflight-api.vercel.app serves 3 paid API services for AI agents, indexed by Zero. Each is callable per call with payment handled by Zero.

Canonical page: https://www.zero.xyz/host/email-preflight-api.vercel.app
Live health (JSON, refreshed every minute): https://www.zero.xyz/host/email-preflight-api.vercel.app/health.json

## Services

- [Agent Preflight APIs – Email HTML Validator](https://www.zero.xyz/c/agent-preflight-apis-email-html-validator-fbca8b79/llms.txt): $0.01/call via x402. Deterministically validates email HTML for deliverability issues, clipping risk, and compatibility problems before an agent sends a campaign or transactional message.
- [x402 Payment Preflight Shortlist](https://www.zero.xyz/c/x402-payment-preflight-shortlist-d219edea/llms.txt): $0.005/call via x402. Searches the Coinbase CDP Bazaar for x402-payment-gated endpoints matching a described need, probes live candidates for valid 402 challenges, and recommends the best passing candidate with full payment details.
- [x402 Preflight Checker](https://www.zero.xyz/c/x402-preflight-checker-2b748e5c/llms.txt): $0.003/call via x402. Inspects a live x402 v2 payment challenge before an agent commits to payment, verifying price, network, payee, resource binding, timeout, and Bazaar metadata without paying or forwarding credentials.

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

- [Zero catalog index](https://www.zero.xyz/llms.txt)