ContactLint

ContactLint MCP Server (contactlint-mcp)

ContactLint checks email addresses and phone numbers before your AI agent saves or uses them. You can run it as a local stdio MCP server (contactlint-mcp, reading CONTACTLINT_API_KEY from the environment) or connect directly to the hosted Streamable HTTP endpoint (https://contactlint.com/mcp).

• Local stdio binary: contactlint-mcp (./bin/contactlint-mcp.mjs)
• Hosted endpoint: https://contactlint.com/mcp (Streamable HTTP, JSON-RPC over POST)
• Website: https://contactlint.com/
• MCP guide: https://contactlint.com/email-validation-mcp-server
• OpenAPI (REST API): https://contactlint.com/openapi.json
• MCP Registry: com.contactlint/contactlint

Tools

Tool	Input	What it does
validate_email	email	Checks syntax, MX and A records over DNS-over-HTTPS, known disposable domains, role addresses (admin@, no-reply@) and free providers, and suggests a fix when the domain looks like a typo of a major provider (gmial.com).
validate_emails	emails (1 to 50 addresses)	Same checks as validate_email for up to 50 addresses in one call. Returns one result per address in the same order plus a summary of verdicts.
validate_phone	phone, optional country (ISO 3166-1 alpha-2 default region, for example US)	Parses and validates a phone number: valid and possible flags, line type, region, E.164, national and international formats.

ContactLint does not connect to mail servers (no SMTP probing), so it cannot confirm that a mailbox exists or detect catch-all domains.

initialize and tools/list work without a key, so clients and directory scanners can read the tool list. tools/call requires a ContactLint API key (100 free checks per month, no card required).

Option 1: Local stdio MCP server (recommended for registries & desktop clients)

The local stdio server (bin/contactlint-mcp.mjs) reads your API key from the CONTACTLINT_API_KEY secret environment variable and forwards authenticated tool calls to https://contactlint.com/mcp.

Environment variables

Variable	Required	Secret	Description
CONTACTLINT_API_KEY	Yes	Yes	Your ContactLint API key, sent as Authorization: Bearer <key>. Get a free key (100 checks/month, no card) at https://contactlint.com/signup
CONTACTLINT_MCP_URL	No	No	Optional endpoint override (defaults to https://contactlint.com/mcp)

Client configuration (stdio via npx)

{
  "mcpServers": {
    "contactlint": {
      "command": "npx",
      "args": ["-y", "github:zksyncer/contactlint"],
      "env": {
        "CONTACTLINT_API_KEY": "YOUR_API_KEY"
      }
    }
  }
}

Or when installed locally (npm install -g github:zksyncer/contactlint or pnpm add contactlint-mcp):

{
  "mcpServers": {
    "contactlint": {
      "command": "contactlint-mcp",
      "env": {
        "CONTACTLINT_API_KEY": "YOUR_API_KEY"
      }
    }
  }
}

Option 2: Hosted Streamable HTTP MCP server

If your MCP client supports custom HTTP headers on remote streamable-http servers, you can connect directly without installing anything:

{
  "mcpServers": {
    "contactlint": {
      "type": "http",
      "url": "https://contactlint.com/mcp",
      "headers": {
        "Authorization": "Bearer YOUR_API_KEY"
      }
    }
  }
}

Billing

• One check per address or number checked. A validate_emails call with 20 addresses uses 20 checks.
• Addresses whose DNS lookup fails come back unknown (dns_error) and are not billed.
• If a key does not have enough checks for a whole validate_emails list, nothing is checked or billed.
• 100 checks per month are free, no card needed.
• Credit packs: 5,000 checks for $9, 25,000 for $35, 100,000 for $99.

Free tools

Free browser tools (disposable email checker, phone number validator, disposable domain list) are at https://contactlint.com/tools

License

MIT, see LICENSE.