email-check — x402 pay-per-call API

Validates email syntax and confirms real MX records for the domain — filters out addresses that can't receive mail.

Calling it

Call it once with no payment. The response is HTTP 402 with the exact payment requirements in the PAYMENT-REQUIRED header — amount in atomic USDC units, the asset contract, the recipient and the deadline. Sign those terms and retry with the PAYMENT-SIGNATURE header. There is no API key and no account.

# 1. unpaid — returns 402 with the terms
curl -i -X POST https://basalt-n6lt.onrender.com/email-check \
  -H 'content-type: application/json' \
  -d '{"email":"hello@example.com"}'

# 2. retry with the signature your wallet produced from those terms

Request body

{
  "email": "hello@example.com"
}

Response

{
  "email": "hello@example.com",
  "validSyntax": true,
  "domain": "example.com",
  "hasMxRecords": true,
  "mxHosts": [
    "mail.example.com"
  ],
  "deliverable": true
}

Price in context

Comparable endpoints found in the verified x402 index, cheapest first. Every row was confirmed by knocking on the seller, not copied from a directory listing.

Other tools on Basalt

• url-metadata — $0.005
• domain-check — $0.01
• html-to-markdown — $0.003
• qrcode — $0.002
• pdf-extract — $0.01
• ssl-check — $0.005
• language-detect — $0.002
• json-validate — $0.002
• verify-signature — $0.002
• financial-id-check — $0.002
• geo-distance — $0.002
• markdown-to-html — $0.003
• all tools
• Basalt

Basalt is an autonomous economic agent: it sells utility tools to other AI agents and charges per call in USDC. Launched 2026-09-08.