Phone StackPhone Stack

AI Phone Agent
Voice Agents With Tool Use

Phone Stack is an AI phone agent platform: voice agents that hold real-time phone conversations and call tools mid-call — booking calendar slots, updating your CRM, sending emails, firing webhooks. One agent profile handles both inbound and outbound. Native speech-to-speech keeps responses sub-second, setup is zero-code via chat, and pricing is all-inclusive from $0.18/minute with 30 free minutes.

Deploy an AI phone agent that holds real conversations, calls tools mid-call (calendar, CRM, webhooks), and runs both inbound and outbound from a single profile. Sub-second latency, full REST API.

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What is an AI phone agent?

An AI phone agent is a voice agent that holds real-time spoken phone conversations and takes structured actions during the call — booking a meeting, looking up a record, updating your CRM, firing a webhook. The “agent” framing matters: unlike a static voicebot, an AI phone agent reasons, plans, and uses tools.

Phone Stack AI phone agents run on Google Gemini Live for sub-second voice latency, Anthropic Claude for high-quality reasoning and tool use, and Twilio for the telephony layer. The result is a phone agent that sounds human and actually completes the work.

What an AI phone agent can do

Calendar booking

Live availability check, slot booking, confirmation send

CRM writeback

Create + update records in HubSpot, Salesforce, or any REST CRM

Knowledge-base lookup

Cite docs and answer accurately mid-conversation

Payment links

Send a Stripe link via SMS while on the call

Email send

Trigger personalized follow-up email from a template

Custom webhooks

Fire any HTTP request — your backend, your logic

How AI phone agents work

  1. 1.Voice in. Twilio routes the audio over a WebSocket to the agent runtime.
  2. 2.Reason. Gemini Live streams the conversation; Claude handles tool decisions.
  3. 3.Act. The agent calls tools (calendar, CRM, webhook) and incorporates results into the reply.
  4. 4.Voice out. Sub-second response with native barge-in support.
  5. 5.Wrap. Recording, transcript, summary, scoring, and CRM update — all automatic.

Part of the Phone Stack AI call center

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Build your first AI phone agent today

15-minute setup. 30 free minutes. Full API.

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