ContactLint: email and phone validation API

ContactLint checks email addresses and phone numbers over a simple HTTP API. It is built for signup forms, CRM cleanup, and AI agents that need to confirm contact data before using it.

Get a free API key. 100 checks per month, no card required.

What it checks

Email

Practical RFC syntax
MX and A records via DNS-over-HTTPS
Disposable domain list
Role addresses such as admin@ and info@
Free mail provider flag

It never opens an SMTP connection to the mailbox.

Phone

Parsing with libphonenumber metadata
Valid and possible flags
Line type and region
E.164, national, and international formats

Endpoints

Method	Path	Purpose
POST	/v1/email/validate	Validate one email. Body: {"email": "..."}
POST	/v1/phone/validate	Validate one phone. Body: {"phone": "...", "country": "US"}
GET	/v1/usage	Free checks used this month and credit balance
POST	/mcp	MCP server with tools validate_email and validate_phone
GET	/openapi.json	OpenAPI 3.1 spec

Send your key as Authorization: Bearer YOUR_KEY or x-api-key.

curl -X POST https://contactlint.com/v1/email/validate \
  -H "Authorization: Bearer YOUR_KEY" \
  -H "content-type: application/json" \
  -d '{"email":"someone@example.com"}'

Use it from an AI agent (MCP)

Point any MCP client that supports streamable HTTP at https://contactlint.com/mcp with the header Authorization: Bearer YOUR_KEY. Tools: validate_email, validate_phone. Each tool call uses one check.

Pricing

Plan	Checks	Price
Free	100 per month	$0
Credit pack	5,000	9
Credit pack	25,000	35
Credit pack	100,000	99

Buy credits. Unused credits are refundable within 14 days of purchase.

Errors and limits

401 missing or invalid key. 402 free checks used up and no credits. 429 more than 60 requests per minute per key. 400 bad input.

Data sources

Disposable domains come from the disposable-email-domains project (CC0 1.0). Phone parsing uses libphonenumber-js (MIT). DNS lookups use Cloudflare DNS-over-HTTPS.