NumbersOnline
For developers

The phone-number trust & intelligence API.

Send an E.164 number and get caller-name context where available, line type, carrier, and an optional low-confidence supplementary risk signal — for softphones, PBXs, SBCs, AI voice agents, chatbots, and CRMs. Copy-paste artifacts, a rate-limited free tier, and fail-open behaviour on live call paths. Your system keeps every routing, labeling, dialing, and blocking decision.

Start here
Get a free API key

Self-service, instant, no card and no sales call. Every endpoint works on the free tier (rate-limited). The key is shown exactly once and stored only as a hash, so save it.

No card, no sales call. Free tier: 10 lookups/min · 50/day, plus 10 reports/day, pooled per account. The key is shown once, so save it. Prefer to manage keys, balance and top-ups while signed in? Use the dashboard →

What a key gets you

  • Caller-name context (CNAM) where available — a missing name means “unknown”, never a negative signal.
  • Line type, carrier and validity, keyed on a single E.164 primitive.
  • An optional, low-confidence supplementary spam-risk signal — advisory, never a verdict.
  • Inbound caller intelligence, an MCP server and Vapi / Retell webhooks for AI voice agents.
  • A do-not-call scrub for outbound dialling and a ClearIP-compatible SBC / SIP redirect decision.
  • Tamper-evident signed receipts (Ed25519) you can retrieve later as evidence.

Free / unverified accounts share a pooled allowance — 10 lookups/min, 50 lookups/day, and 10 reports/day, pooled across your account’s keys; other endpoints have documented per-key fair-use windows. Verify a business number to raise the pooled limit (+2,000 lookups/day each), or add prepaid credit ($5–$500) to burst past it on the metered standard tier. See pricing for the full picture.

Where to next

Choose an integration
Drop-in, copy-paste artifacts for FreePBX, FreeSWITCH / FusionPBX, 3CX, MicroSIP, Vapi, Retell, and a Kamailio / OpenSIPS / dSIPRouter SBC recipe.
Browse platforms
Copy an AI-agent prompt
Hand a ready-made prompt to Claude Code, Cursor, Windsurf or Copilot and wire a softphone, chatbot, AI voice agent, or CRM without reading the whole API first.
Get the prompts
Read the API reference
Every endpoint in onboarding order with a live keyless try-it, plus the machine-readable OpenAPI spec and llms.txt for your coding agent.
Open the docs

A supplementary signal, not a verdict

Numbers Online returns an advisory caller name and a low-confidence, supplementary spam-risk signal. It never asserts that a call is lawful, unlawful, “safe”, or otherwise, and a missing name means “unknown”, never a negative signal. On any live-call path the integration is built to fail open: a slow or failing lookup advances the call unchanged, never delays or drops it. Your system keeps every routing, labeling, dialing, and blocking decision and remains responsible for compliance. Point your coding agent at the machine-readable llms.txt and the authoritative OpenAPI spec for the full contract.