Twilio Serverless function Retell AI

Connect you existing Twilio account to Retell AI with a simple serverless function.

This project is simply one function that you can configure on your Twilio phone number.

Note This is a typescript project, the output is in the dist/ folder

Configure the retell agent_id as either an environment variable or a query parameter. The query parameter will take precedent.

Setup Instructions

Create a Twilio account
Create a Retell account
Clone this repo with gh repo clone chaosloth/twilio-retell-serverless (or) git clone https://github.com/chaosloth/twilio-retell-serverless.git
Make a copy of the .env.example file as .env and populate the values
Navigate to the newly cloned folder, e.g. cd twilio-retell-serverless
Install dependencies with npm i or yarn
Build the project with npm run build or yarn build
Deploy the project to Twilio with npm run deploy or yarn deploy
You can also run locally with twilio serverless start --functions-folder dist/functions --ngrok="" to start a local ngrok server

Environment file

Configure you environment file as follows, inserting the respective values for your account on Twilio and Retell.ai

#
# Twilio Account SID
#
ACCOUNT_SID=
AUTH_TOKEN=

#
# Retell.AI API key
#
RETELL_API_KEY=

#
# Retell.AI Agent ID
#
RETELL_AGENT_ID=

#
# Twilio Segment
#
SEGMENT_PROFILES_API_BASE_URL=https://profiles.segment.com/v1
SEGMENT_API_ACCESS_TOKEN=
SEGMENT_SPACE_ID=
SEGMENT_WRITE_KEY=

Twilio Segment

Retell bots an take advantage of Twilio Segment CDP integration by looking up customer information, updating customer information and adding data to the customer's profile.

We can do this by using tools defined in this project. Below are a list of tools to perform the respective action.

Tool	Path	Purpose
Customer lookup	/lookup	Find the customer's profile base on the incoming number
Update details	/save_customer	Store the customer information against their profile
Add event	/add_event	Add a tracking event for this customer

Tool: Customer lookup

The customer lookup tool doesn't require any tool body as the required data is passed in metadata (assuming that you are using the /start function that is also in this project).

Tool: Update details

The update details tool has the following definition, you can adjust as required.

{
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Name of the customer"
    },
    "phone": {
      "type": "string",
      "description": "E.164 phone number of the customer"
    },
    "address": {
      "type": "string",
      "description": "Customer delivery or billing address"
    }
  },
  "required": [
    "name",
    "phone"
  ]
}

Tool: Add Event

The add event (place order) tool has the following definition, you can adjust as required.

Note that the tool name (e.g. place_order) as defined in Retell is used as the event name.

Additionally, note that you can used this same tool definition again to send events with a difference event name.

{
  "type": "object",
  "properties": {
    "summary": {
      "type": "string",
      "description": "Summary of the pizza order including all items"
    },
    "total": {
      "type": "string",
      "description": "Total price of the order"
    },
    "timestamp": {
      "type": "string",
      "description": "String representation of the time of this order"
    }
  },
  "required": [
    "summary",
    "total",
    "timestamp"
  ]
}

Twilio Studio

Redirect back to Twilio Studio

To redirect the call back to Twilio Studio we send the call to a Twilio App

First create the Studio flow and get the Webhook URL.

Create the app and use this Studio Webhook URL

Retell Tools

Create a tool in RetellAI that calls the redirect URI passing the Application SID as a parameter

The tool definition is like this:

{
  "type": "object",
  "properties": {
    "Summary": {
      "type": "string",
      "description": "Summary of the conversation so far"
    }
  },
  "required": [
    "Summary"
  ]
}