Phone number, SMS and voice APIs for AI agents
Carrier APIs for numbers and texts, and voice-agent platforms that let an AI answer and place calls.
4 tools, listed alphabetically. Prices and features checked 2026-10-17 on each vendor's own pages; “not verified” means we could not confirm it.
Short answer: For numbers and SMS, Telnyx lists $0.004 per US message part plus carrier fees, against Twilio's $0.0083 per segment; numbers start at $1.00/month (Telnyx) and $1.15/month (Twilio local). For voice agents, Vapi charges $0.05/min for hosting plus your chosen speech, model and voice providers. Retell lists $0.07–$0.31/min all in, with $10 of free credit.
| Tool | Free tier | Entry paid price | Meter | MCP server | Open source | Phone numbers |
|---|---|---|---|---|---|---|
| Retell AI | $10 free credits; 20 concurrent calls included [source, checked 2026-10-17] | Pay as you go: $0.07–$0.31 per minute for voice agents; chat agents from $0.002 per message [source, checked 2026-10-17] | Per minute: Retell voice infra $0.055/min plus model and voice costs [source] | not verified | not verified | not verified |
| Telnyx | No platform fee; pay as you go [source, checked 2026-10-17] | SMS $0.004 per message part + carrier fee; Voice API $0.002/min + SIP trunk fee; numbers from $1.00/month [source, checked 2026-10-17] | Per message part, per minute and per number; carrier fees passed through at cost [source] | Official MCP server (TypeScript) in telnyx-node [source] | not verified | From $1.00 per number per month [source] |
| Twilio | Free trial, no credit card [source, checked 2026-10-17] | US SMS $0.0083 per segment sent or received; local number $1.15/month; local calls $0.0140/min out, $0.0085/min in [source, checked 2026-10-17] | Per message segment, per call minute and per number per month; carrier fees vary [source] | Twilio Labs MCP server (alpha, MIT) [source] | not verified | Local $1.15/month, toll-free $2.15/month (US) [source] |
| Vapi | $5 free credits, 1 Vapi phone number, 4 concurrent calls [source, checked 2026-10-17] | Pay as you go from $0.05/min plus providers; Core package $29/month: 5 numbers, 10 concurrent calls [source, checked 2026-10-17] | $0.05/min Vapi hosting plus transcriber, model, voice and telephony costs [source] | Vapi MCP server [source] | not verified | not verified |
| Tool | Best for | Compliance | Data retention |
|---|---|---|---|
| Retell AI | Teams that want an all-in per-minute price for voice agents and SOC 2 and HIPAA without a separate add-on fee. | SOC 2 certified; HIPAA with BAA listed [source] | not verified |
| Telnyx | Cost-sensitive SMS and voice at volume, where you want the platform rate and carrier pass-through shown separately. | HIPAA listed on the pricing pages [source] | not verified |
| Twilio | Teams that want the widest set of channels (SMS, voice, WhatsApp, email) on one account with pay-as-you-go rates. | not verified | not verified |
| Vapi | Developers building voice agents who want to choose their own speech, model and voice providers. | HIPAA add-on with BAA: $2,000/month [source] | Raw data: 14 days (no package), 30 days (Core), 180 days (Pro) [source] |
What to check before you pick one
- Build or buy the voice stack: Twilio and Telnyx give you numbers and calls; Vapi and Retell run the AI conversation.
- Per-minute total: Vapi's $0.05 is hosting only, and providers add the rest. Retell's range already includes model and voice.
- US messaging rules: A2P 10DLC registration fees apply on Twilio (per its pricing page), and carrier fees apply on both carriers.
- Compliance: Retell lists SOC 2 and HIPAA; Vapi sells HIPAA as a $2,000/month add-on; Telnyx lists HIPAA.
- Call recording and consent laws vary by country and state; check them before an agent places outbound calls.
FAQ
Can an AI agent have a phone number?
Yes. Buy a number from Twilio or Telnyx through the API, or use Vapi's included numbers (1 free, 5 on Core), and attach a voice agent or an SMS webhook to it.
What does an AI phone call cost per minute?
On Retell, $0.07–$0.31 per minute depending on model and voice. On Vapi, $0.05 per minute hosting plus provider costs; Vapi's own example estimates $82–129 for 1,000 minutes.
Twilio or Telnyx for SMS?
Telnyx's listed US rate is lower ($0.004 per part plus carrier fee, against $0.0083 per segment on Twilio). Twilio offers more channels on one account. See our Twilio vs Telnyx page.
Comparisons and alternatives
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