Guides · API

Phone number validation API

Phone number validation for any country: valid and possible checks against allocated number ranges, E.164, international and national formatting, country and calling code, and line type (mobile, landline, VoIP, toll-free, premium rate, shared cost) with an SMS-capable hint. For signup, KYC, CRM cleanup, SMS and calling agents. National numbers accepted with a country code, e.g. 0612345678 with country=NL.

0.003 USDC per call · GET /v1/phone/verify · free preview at /v1/phone/verify/preview

Parameters

Name	Required	Description
`phone`	yes	Phone number, international (+31612345678) or national with country, e.g. 0612345678
`country`	no	Optional ISO country for national numbers, e.g. NL, DE, GB

Example request

curl "https://factline.dev/v1/phone/verify?phone=%2B31612345678"
# 402 Payment Required: pay with an x402 client (USDC on Base), or send
# Authorization: Bearer <your Factline API key>

Example response

{
  "input": "+31612345678",
  "valid": true,
  "possible": true,
  "e164": "+31612345678",
  "international": "+31 6 12345678",
  "national": "06 12345678",
  "country": "NL",
  "country_name": "Netherlands",
  "calling_code": "+31",
  "line_type": "mobile",
  "sms_capable": true,
  "explain": {
    "valid": "The number matches an allocated number range for its country (not whether it is currently in service).",
    "line_type": "From the number range. Ported numbers keep their range type; carrier is not reported."
  },
  "source": "Google libphonenumber metadata"
}

Use it from an AI agent

Agents with an x402 wallet call the URL directly and pay per request. Assistants that speak MCP connect to https://factline.dev/mcp. Full reference: docs, OpenAPI, llms.txt. Businesses: API keys with a free trial.

Questions

How much does the Phone number validation cost?

0.003 USDC per call, paid per request with x402 (no account), or included in a Factline API key plan with a free trial. Calls that fail are not charged.

Can I try it for free?

Yes: GET /v1/phone/verify/preview with the same parameters validates your input and shows what the paid answer contains, at no cost.

Where does the data come from?

Official public registers and open data, named with their licence in every response (source field) and at /.well-known/x402-license-provenance.