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📞 Build, test, deploy, and monitor AI phone agents.

Introduction

Deploy your first phone agent in 5 minutes.

Build your first phone agent in 5 minutes

Learn how to use Retell's Node.js and Python SDKs

SDKs

Step 2: Configure the basic settings

Choose a custom voice

Add pause or read slowly

Pronounce the phone numbers correctly

Add custom pronunciation

Automatically normalize text for speech

Add backchannel

Handle background noise

Configure your AI agent to detect and handle voicemails automatically

Handle voicemail

Knowledge Base

Learn how to personalize your agent's responses using dynamic variables

Dynamic Variables

Best Practices

Learn how to effectively test and debug your AI agents using the LLM Playground

LLM Playground

A step by step guide to buy a number from Retell

Purchase phone number

A step by step guide to integrate custom telephony providers

Overview

A step by step guide to make & receive phone calls with Retell managed numbers & imported numbers

Make & receive phone calls

Add a business profile

Apply for verified phone number

Apply for branded call

A step by step guide to create a web call with agent using frontend Web SDK

Connect to web call

Understand the constraints and limitations of the agents.

Understand concurrency & limits

Monitor calls via dashboard

Register the webhook

Secure the webhook

Define the information you want to extract

Consume the analysis data

Check estimated latency

Check actual latency

Follow these steps to resolve high end-to-end latency issues.

Troubleshoot high latency

Troubleshooting Transcript Accuracy

How to fix when your AI agent gives incorrect responses

Debug wrong response

Debug call transfer failure

How to locate and address issues while developing with Retell.

Debug call disconnection

Workspace

Account

Billing

Manage API Keys

Custom LLM Overview

Setup WebSocket Server

Integrate LLM

Integrate Function Calling

Troubleshooting Guide

Custom LLM Best Practices

Audio Basics

Create Phone Call

Create Web Call

Get Call

List Calls

Create Retell LLM

Retrieve details of a specific Retell LLM

Get Retell LLM

List Retell LLMs

Update Retell LLM

Delete Retell LLM

Create Agent

Get Agent

List Agents

Update Agent

Delete Agent

Create Phone Number

Retrieve details of a specific phone number

Get Phone Number

List Phone Numbers

Update agent bound to a purchased phone number

Update Phone Number

Delete Phone Number

Create Knowledge Base

Retrieve details of a specific knowledge base

Get Knowledge Base

List Knowledge Bases

Delete Knowledge Base

Get Voice

List Voices

Get the current concurrency and concurrency limit of the org

Get Concurrency

Import a phone number from custom telephony & Bind agents

Import Phone Number

Register a new phone call for custom telephony

Register Phone Call

Retell AI connects with your server, and get responses / actions from your custom LLM.

LLM WebSocket

Migration guide

Create Phone Call (Deprecated)

Register Call To Get CallId To Establish Connection

Register Call (Deprecated)

Get Call (Deprecated)

List Calls (Deprecated)

Retell AI connects with user audio source, read and send audio bytes through this WebSocket.

Get Started

Build

Test

Deploy

Monitor

Reliability

Accounts and Workspace

Advanced Topics

Network Ecosystem

Web Call