> ## Documentation Index
> Fetch the complete documentation index at: https://docs.thinnest.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Voice Tools Overview

> 44 voice features that give your agent superpowers during live calls — call control, authentication, payments, analytics, compliance, and more.

# Voice Tools & Features

Voice tools extend your agent's abilities during a live phone call. Unlike general tools (Google Calendar, Sheets, etc.), voice tools interact directly with the call itself — ending it, transferring it, sending an SMS mid-conversation, collecting payments, or authenticating callers.

thinnestAI provides **44 voice features** organized into categories below. Some features expose callable tools to the LLM (the agent decides when to use them), while others inject behavior via the system prompt or run automatically.

***

## Call Control

Core tools for managing the call lifecycle.

| Tool                                                       | What It Does                                                    | LLM Tool                                 |
| ---------------------------------------------------------- | --------------------------------------------------------------- | ---------------------------------------- |
| [End Call](/docs/voice/tools/end-call)                     | Programmatically end a call with configurable farewell messages | `end_call`                               |
| [Transfer Call](/docs/voice/tools/transfer-call)           | Hand off to a human agent, department, or another AI agent      | `transfer_to_{agent}`                    |
| [Hold / Resume](/docs/voice/tools/hold-resume)             | Put the caller on hold while looking up information             | `put_caller_on_hold`, `resume_from_hold` |
| [Conference Calling](/docs/voice/tools/conference-calling) | Add a third party (supervisor, specialist) to the call          | `start_conference`                       |
| [DTMF Input](/docs/voice/tools/dtmf)                       | Send or receive dial-tone keypresses during a call              | via config                               |
| [Voicemail Drop](/docs/voice/tools/voicemail-drop)         | Leave a pre-recorded message when voicemail is detected         | `detected_answering_machine`             |

***

## Communication

Send messages and visual content to the caller during or after the call.

| Tool                                                         | What It Does                                                       | LLM Tool           |
| ------------------------------------------------------------ | ------------------------------------------------------------------ | ------------------ |
| [SMS Mid-Call](/docs/voice/tools/sms-mid-call)               | Send a text message to the caller during a live call               | `send_sms`         |
| [Visual IVR](/docs/voice/tools/visual-ivr)                   | Send a link to the caller's phone for forms, maps, or complex info | `send_visual_link` |
| [Post-Call Follow-Up](/docs/voice/tools/post-call-follow-up) | Trigger emails, SMS, or webhooks after the call ends               | automatic          |

***

## Authentication & Security

Verify caller identity and enforce compliance.

| Tool                                                          | What It Does                                                   | LLM Tool                                             |
| ------------------------------------------------------------- | -------------------------------------------------------------- | ---------------------------------------------------- |
| [Caller Authentication](/docs/voice/tools/caller-auth)        | Verify identity via PIN, DOB, passphrase, or custom credential | `verify_caller_identity`, `fail_caller_auth`         |
| [Voice Biometrics](/docs/voice/tools/voice-biometrics)        | Verify caller identity using voiceprint analysis               | `verify_voice_identity`                              |
| [Voice Approvals (HITL)](/docs/voice/tools/voice-approvals)   | Get verbal confirmation before high-stakes actions             | `request_voice_approval`, `record_approval_decision` |
| [Compliance & Consent](/docs/voice/tools/compliance-security) | Recording consent, guardrails, hallucination prevention        | via config                                           |
| [Do-Not-Call List](/docs/voice/tools/do-not-call)             | Check numbers against DNC lists before outbound calls          | `check_dnc_list`                                     |

***

## Business Actions

Tools that perform real-world actions during the call.

| Tool                                                         | What It Does                                                 | LLM Tool                                 |
| ------------------------------------------------------------ | ------------------------------------------------------------ | ---------------------------------------- |
| [Appointment Booking](/docs/voice/tools/appointment-booking) | Check availability and book calendar appointments            | `check_availability`, `book_appointment` |
| [Payment Processing](/docs/voice/tools/payment-processing)   | Collect PCI-compliant payments via Stripe or custom provider | `collect_payment`                        |
| [MCP Server Integration](/docs/voice/tools/mcp-voice)        | Call external tools via Model Context Protocol               | `mcp_call`                               |

***

## Recording & Monitoring

Record, monitor, and analyze calls in real time.

| Tool                                                                                | What It Does                                   | LLM Tool   |
| ----------------------------------------------------------------------------------- | ---------------------------------------------- | ---------- |
| [Call Recording](/docs/voice/tools/call-recording)                                  | Record calls with consent management           | via config |
| [Call Queue](/docs/voice/tools/call-queue)                                          | Queue callers when all agents are busy         | via config |
| [Live Call Monitoring](/docs/voice/tools/analytics-monitoring#live-call-monitoring) | Supervisors can listen to or join active calls | via config |

***

## Analytics & Post-Call

Track performance, detect gaps, and sync with external systems.

| Tool                                                             | What It Does                                                   | LLM Tool                 |
| ---------------------------------------------------------------- | -------------------------------------------------------------- | ------------------------ |
| [Conversion Tracking](/docs/voice/tools/conversion-tracking)     | Record conversion events when goals are met                    | `track_conversion`       |
| [Post-Call Survey](/docs/voice/tools/post-call-survey)           | Ask a survey question before ending the call                   | `record_survey_response` |
| [Sentiment Escalation](/docs/voice/tools/sentiment-escalation)   | Detect negative sentiment and escalate to a human              | `escalate_sentiment`     |
| [Analytics & Monitoring](/docs/voice/tools/analytics-monitoring) | Call scoring, CRM sync, knowledge gap detection, speed-to-lead | automatic                |

***

## Voice & Language

Control how the agent sounds and handles multiple languages.

| Tool                                                        | What It Does                                                               | LLM Tool          |
| ----------------------------------------------------------- | -------------------------------------------------------------------------- | ----------------- |
| [Multilingual Auto-Switch](/docs/voice/tools/multilingual)  | Detect language and switch TTS/STT mid-call                                | `switch_language` |
| [Call Experience Features](/docs/voice/tools/call-features) | Pace control, silence fillers, backchanneling, greeting variants, and more | via config        |

***

## Adding Voice Tools to Your Agent

Voice tools are configured in the **Voice Settings** section of your agent, separate from general tools.

### Via the Dashboard

1. Open your agent in the dashboard.
2. Scroll to the **Voice Settings** section.
3. Enable the tools you need (e.g., toggle **End Call**, **Transfer**, **DTMF**).
4. Configure each tool's settings (e.g., transfer destination number, SMS template).
5. Click **Save**.

### Via the API

```json theme={null}
{
  "voiceEnabled": true,
  "endCallEnabled": true,
  "interruptionConfig": { "enabled": true, "threshold": 0.5 },
  "recordingConfig": { "enabled": true },
  "silenceConfig": {
    "unresponsiveTimeoutSeconds": 30,
    "fillersEnabled": true,
    "fillerPhrases": ["Let me check that for you...", "One moment please..."]
  },
  "webhookConfig": {
    "url": "https://your-server.com/webhook",
    "events": ["call_started", "call_ended"]
  }
}
```

See the [Create Agent API](/api-reference/agents/create) for the full voice configuration reference.

## How Voice Tools Work

During a live call, your AI agent decides when to use a voice tool based on conversation context and your instructions. For example:

* The caller asks to speak to a manager -> agent triggers **Transfer Call**
* The caller says "goodbye" -> agent triggers **End Call**
* The caller asks for a confirmation link -> agent triggers **SMS Mid-Call**
* Voicemail detected on outbound call -> agent triggers **Voicemail Drop**
* Caller's sentiment drops significantly -> agent triggers **Sentiment Escalation**
* Caller wants to make a payment -> agent triggers **Payment Processing**

## General vs. Voice Tools

|                   | General Tools                       | Voice Tools                             |
| ----------------- | ----------------------------------- | --------------------------------------- |
| **Scope**         | Any agent (chat, voice, workflow)   | Voice agents only                       |
| **Examples**      | Google Calendar, Gmail, Sheets, CRM | End Call, Transfer, DTMF, SMS, Payments |
| **Configured in** | Tools tab                           | Voice Settings                          |
| **Trigger**       | Agent decides based on context      | Agent decides + call events             |

Your agent can use both general tools and voice tools simultaneously. For example, during a call the agent might look up a calendar slot (general tool) and then send an SMS confirmation (voice tool).