### Answer Setting up a call agent in Retell AI involves a few key steps: ## 1. Create Your Agent First, build your agent in the Retell AI dashboard using either: - Single/Multi-Prompt mode - for simpler conversational flows - Conversation Flow - a visual node-based editor for guided, multi-path dialogues [(1) ]() ## 2. Connect Telephony You have several options for telephony: Option A: Use Retell's Built-in Numbers - Purchase a phone number directly from Retell (including toll-free numbers) Option B: Custom Telephony via SIP Trunking Connect your own telephony provider (Twilio, Telnyx, Vonage, etc.) using one of two methods: [(2) ]() - Elastic SIP Trunking (recommended) - Connect your provider's SIP trunk directly to Retell - Dial to SIP URI - Your system dials to

sip:{call_id}@sip.retellai.com

## 3. Make Outbound Calls via API Once set up, you can create outbound calls programmatically: [(3) ]()

javascript
import Retell from 'retell-sdk';
const client = new Retell({
  apiKey: 'YOUR_RETELL_API_KEY',
}) ;
const phoneCallResponse = await client.call.createPhoneCall({
  from_number: '+14157774444',
  to_number: '+12137774445',
}) ;

For Twilio-specific setup, there's a detailed guide available at [Twilio Integration Docs]() . [(4) ]() Check out these potentially useful sources for more details: - [Custom Telephony Overview]() - [Create Phone Call API]()

​ To learn more, see the sources I considered: [[1] Platform Changelogs | Retell AI](https://www.retellai.com/changelog) [[2] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[3] Create Phone Call](https://docs.retellai.com/api-references/create-phone-call) [[4] Discord message from @artiombic on 2025-08-30](https://discord.com/channels/1186424376300679209/1186462578310910112/1411464530869092523) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.