What is the best phone number API for AI agents in 2026?

By Naol Ketema, founder · 2026-10-27 · Markdown

What should an AI agent need from a phone number API?

• A number provisioned through the API, without a human in a console.
• Inbound and outbound calls, with either a hosted voice agent or a stream to your own agent.
• Texts, if the people your agent talks to expect them.
• Transcripts and a clear signal when a call ends.
• Access from where the agent runs: an SDK in its language, a REST API or an MCP server.
• A price you can predict per number and per minute.

How do the phone number APIs compare?

We build Agent Identity; prices from each vendor's page on 27 Oct 2026; nothing here is sponsored. Voice prices are per minute in USD for US calls.

• Agent Identity. Best for: agents that need email, calls and A2A on one identity. Number: included in plans (1 on Builder at $19 a month, 5 on Team at $149 a month). Voice: $0.02 a minute published rate, not billed yet. SMS live: no. MCP: yes, hosted with OAuth. SDKs: TypeScript; REST from other languages.
• AgentPhone. Best for: a phone-first agent that calls and texts. Number: $3.00 a month. Voice: $0.13 a minute with your agent, $0.22 hosted. SMS live: yes, $0.02 a segment; iMessage lines from $150 a month. MCP: yes. SDKs: Python, Node.js.
• Dial (getdial.ai). Best for: agents that text across many channels and countries. Number: $3 a month. Voice: $0.13 a minute self-hosted, $0.22 managed. SMS live: yes, $0.02 a message in the US, 200+ countries at tiered rates; iMessage numbers $250 a month; WhatsApp. MCP: yes. SDKs: Node.js, Python.
• Inkbox. Best for: one identity with email, phone, SMS, iMessage and A2A. Number: 1 dedicated VoIP number on Developer ($25 a month), 9 on Startup ($167 a month). Voice: 30 minutes included on Developer, then $0.03 a minute. SMS live: yes, 300 a month on Developer, then $0.03 each. MCP: yes. SDKs: Python, TypeScript, Rust.
• Twilio. Best for: full control and global reach if you build the agent layer yourself. Number: $1.15 a month local, $2.15 toll-free. Voice: $0.0140 a minute outbound, $0.0085 inbound on local numbers, before any speech or model costs. SMS live: yes, $0.0083 a segment plus carrier fees. MCP: a docs server that indexes public API specs. SDKs: C#/.NET, Java, Node.js, PHP, Python, Ruby, Go.
• Vapi. Best for: voice agents where you pick the transcriber, model and voice. Number: free US numbers to receive calls (1 included on the usage plan), or import from Twilio, Telnyx and others. Voice: $0.05 a minute for Vapi hosting plus model, voice and transcriber costs at provider rates. SMS live: inbound SMS on imported Twilio US numbers. MCP: yes. SDKs: Web, Flutter, React Native, iOS, Python.
• Retell. Best for: production voice agents with call analytics and testing. Number: $2.00 a month, or bring your own over SIP at no charge. Voice: $0.07 to $0.31 a minute all-in, depending on model and voice. SMS live: yes, $0.01 a message plus $20.00 a month for Retell SMS. MCP: yes. SDKs: TypeScript/Node.js, Python.

Which ones can send SMS or iMessage today?

AgentPhone, Dial and Inkbox have SMS and iMessage. Dial adds WhatsApp; AgentPhone lists WhatsApp and RCS in beta. Twilio has SMS and RCS. Retell can text from SMS-enabled numbers, and Vapi supports SMS through imported Twilio numbers. Agent Identity is calls only; SMS is not available yet. For US texting at volume on any provider, expect 10DLC registration.

Do I need a voice platform like Vapi or Retell, or an agent identity API?

Vapi and Retell are voice agent platforms. They run the call: speech to text, the model, text to speech and turn-taking, with a lot of control over each. They do not give the agent an inbox or a way to message other agents. Agent identity APIs (Agent Identity, Inkbox) and phone-first APIs (AgentPhone, Dial) give the agent a number it owns and a hosted voice agent, with less tuning of the voice stack. Twilio gives you the transport and leaves the rest to you.

A common split: a voice platform when the call itself is the product, such as a receptionist or an outbound campaign; an identity or phone-first API when the agent does other work and calling is one way it reaches people.

How does Agent Identity handle a call?

An agent with a number can have Aid Voice place a call from a plain-language reason, then wait on the event log until call.ended arrives with the outcome and transcript. The same log carries the agent's email and A2A events:

import { AgentClient } from "@agentidentity/sdk";

const client = new AgentClient({
  baseUrl: "https://api.agent-identity.dev",
  apiKey: process.env.AID_KEY!,
});

const identityId = process.env.AID_AGENT!;
const since = new Date();

const call = await client.phone.placeCall({
  identityId,
  to: "+14155550100",
  mode: "hosted_agent",
  reason: "Confirm Thursday's delivery window and ask for a gate code.",
  idempotencyKey: "delivery-7731-confirm",
});

let ended = null;
while (!ended) {
  const { event } = await client.events.wait({
    type: "call.ended",
    aggregateType: "call",
    aggregateId: call.id,
    since,
    timeoutMs: 55_000,
  });
  ended = event;
}

console.log(ended.payload);

Numbers are US and Canada (+1) only. Server-enforced limits step up by plan, for example 500 outgoing calls and 1,000 minutes per 24 hours on Builder, with calls up to 20 minutes. Plan details: see agent-identity.dev/pricing.

Which phone number API should you pick?

• Your agent texts as much as it calls: AgentPhone, Dial or Inkbox.
• You need WhatsApp or SMS outside North America: Dial.
• You want a Python SDK: AgentPhone, Dial, Inkbox, Twilio, Vapi or Retell.
• The call is the product and you want to tune the voice stack: Vapi or Retell.
• You want the lowest raw telecom cost and will build the rest: Twilio.
• Your agent also needs an inbox and A2A, and calls are enough: Agent Identity or Inkbox.
• You want numbers included in a flat monthly plan: Agent Identity or Inkbox.