Inbound Calling

Quickstart handling inbound calls with Vapi.

An inbound call is a phone call that comes “in” towards a phone number, & in our case, our AI assistant will be there to pick up the phone call.

There are 4 steps we will cover to handle our first inbound phone call:

1. Create an Assistant: we will create an assistant & instruct it on how to conduct the call
2. Get a Phone Number: we can either import existing numbers we own, or purchase one through Vapi
3. Attach Our Assistant: we will put our assistant behind the phone number to pick up calls
4. Call the Number: we can then call the number & talk to our assistant

Vapi’s Pizzeria

We will be implementing a simple order-taking assistant that receives customer calls at a pizza shop called “Vapi’s Pizzeria”.

Vapi’s has 3 types of menu items: pizza, sides, & drinks. Customers will be ordering 1 of each.

Customers will order 3 items: 1 pizza, 1 side, & 1 drink. The assistant will pick up the phone & take the customer's order.

Assistant Setup

First we’re going to set up our assistant in the dashboard. Once our assistant’s transcriber, model, & voice are set up, we can call it to place our order.

You can visit your dashboard by going to dashboard.vapi.ai

Sign-up or Log-in to Vapi

If you haven’t already signed-up, you’re going to need an account before you can use the web dashboard. When you visit dashboard.vapi.ai you may see something like this:

Sign-up for an account (or log-in to your existing account) — you will then find yourself inside the web dashboard. It will look something like this:

Your dashboard may look a bit different if you already have an account with assistants in it. The main idea is that we’re in the dashboard now.

Create an Assistant

Now that you’re in your dashboard, we’re going to create an assistant.

Assistants are at the heart of how Vapi models AI voice agents — we will be setting certain properties on a new assistant to model an order-taking agent.

Once in the “Assistants” dashboard tab (you should be in it by-default after log-in), you will see a button to create a new assistant.

Ensure you are in the 'Assistants' dashboard tab, then this button will allow you to begin the assistant creation flow.

After clicking the create new assistant button, you will see a pop-up modal that asks you to pick a starter template. For our example we will start from a blank slate so choose the Blank Template option.

Ensure you are in the 'Assistants' dashboard tab, then this button will allow you to begin the assistant creation flow.

You will then be able to name your assistant — you can name it whatever you’d like (Vapi’s Pizza Front Desk, for example):

This name is only for internal labeling use. It is not an identifier, nor will the assistant be aware of this name.

Name your assistant.

Once you have named your assistant, you can hit “Create” to create it. You will then see something like this:

The assistant overview. You can edit your assistant’s transcriber, model, & voice — and edit other advanced configuration.

This is the assistant overview view — it gives you the ability to edit different attributes about your assistant, as well as see cost & latency projection information for each portion of it’s voice pipeline (this is very important data to have handy when building out your assistants).

Model Setup

Now we’re going to set the “brains” of the assistant, the large language model. We’re going to be using GPT-4 (from OpenAI) for this demo (though you’re free to use GPT-3.5, or any one of your favorite LLMs).

Set Your OpenAI Provider Key (optional)

Before we proceed, we can set our provider key for OpenAI (this is just your OpenAI secret key).

You can see all of your provider keys in the “Provider Keys” dashboard tab. You can also go directly to dashboard.vapi.ai/keys.

Vapi uses provider keys you provide to communicate with LLM, TTS, & STT vendors on your behalf. It is most ideal that we set keys for the vendors we intend to use ahead of time.

We set our provider key for OpenAI so Vapi can make requests to their API.

While we’re here it’d be ideal for you to go & set up provider keys for other providers you’re familiar with & intend to use later.

Set a First Message

Assistants can optionally be configured with a First Message. This first message will be spoken by your assistant when either:

• A Web Call Connects: when a web call is started with your assistant
• An Inbound Call is Picked-up: an inbound call is picked-up & answered by your assistant
• An Outbound Call is Dialed & Picked-up: an outbound call is dialed by your assistant & a person picks up

Note that this first message cannot be interrupted & is guaranteed to be spoken. Certain use cases need a first message, while others do not.

For our use case, we will want a first message. It would be ideal for us to have a first message like this:

Vappy’s Pizzeria speaking, how can I help you?

Some text-to-speech voices may struggle to pronounce ‘Vapi’ correctly, compartmentalizing it to be spoken letter by letter “V. A. P. I.”

Some aspects of configuring your voice pipeline will require tweaks like this to get the target behaviour you want.

This will be spoken by the assistant when a web or inbound phone call is received.

Set the System Prompt

We will now set the System Prompt for our assistant. If you’re familiar with OpenAI’s API, this is the first prompt in the message list that we feed our LLM (learn more about prompt engineering on the OpenAI docs).

The system prompt can be used to configure the context, role, personality, instructions and so on for the assistant. In our case, a system prompt like this will give us the behaviour we want:

You are a voice assistant for Vappy’s Pizzeria,
a pizza shop located on the Internet.

Your job is to take the order of customers calling in. The menu has only 3 types
of items: pizza, sides, and drinks. There are no other types of items on the menu.

1) There are 3 kinds of pizza: cheese pizza, pepperoni pizza, and vegetarian pizza
(often called "veggie" pizza).
2) There are 3 kinds of sides: french fries, garlic bread, and chicken wings.
3) There are 2 kinds of drinks: soda, and water. (if a customer asks for a
brand name like "coca cola", just let them know that we only offer "soda")

Customers can only order 1 of each item. If a customer tries to order more
than 1 item within each category, politely inform them that only 1 item per
category may be ordered.

Customers must order 1 item from at least 1 category to have a complete order.
They can order just a pizza, or just a side, or just a drink.

Be sure to introduce the menu items, don't assume that the caller knows what
is on the menu (most appropriate at the start of the conversation).

If the customer goes off-topic or off-track and talks about anything but the
process of ordering, politely steer the conversation back to collecting their order.

Once you have all the information you need pertaining to their order, you can
end the conversation. You can say something like "Awesome, we'll have that ready
for you in 10-20 minutes." to naturally let the customer know the order has been
fully communicated.

It is important that you collect the order in an efficient manner (succinct replies
& direct questions). You only have 1 task here, and it is to collect the customers
order, then end the conversation.

- Be sure to be kind of funny and witty!
- Keep all your responses short and simple. Use casual language, phrases like "Umm...", "Well...", and "I mean" are preferred.
- This is a voice conversation, so keep your responses short, like in a real conversation. Don't ramble for too long.

You can copy & paste the above prompt into the System Prompt field. Now the model configuration for your assistant should look something like this:

Note how our model provider is set to OpenAI & the model is set to GPT-4.

Transcriber Setup

The transcriber is what turns user speech into processable text for our LLM. This is the first step in the end-to-end voice pipeline.

Set Your Deepgram Provider Key (optional)

We will be using Deepgram (which provides blazing-fast & accurate Speech-to-Text) as our STT provider.

We will set our provider key for them in “Provider Keys”:

Set Transcriber

We will set the model to Nova 2 & the language to en for English. Now your assistant’s transcriber configuration should look something like this:

Note how our transcriber is set to 'deepgram', the model is set to 'Nova 2', & the language is set to English.

Voice Setup

The final portion of the voice pipeline is turning LLM output-text into speech. This process is called “Text-to-speech” (or TTS for short).

We will be using a voice provider called PlayHT (they have very conversational voices), & a voice provided by them labeled Jennifer (female, en-US).

You are free to use your favorite TTS voice platform here. ElevenLabs is another alternative — by now you should get the flow of plugging in vendors into Vapi (add provider key + pick provider in assistant config).

You can skip the next step(s) if you don’t intend to use PlayHT.

Set Your PlayHT Provider Key (optional)

If you haven’t already, sign up for an account with PlayHT at play.ht. Since their flows are liable to change — you can just grab your API Key & User ID from them.

Set Voice

You will want to select playht in the “provider” field, & Jennifer in the “voice” field. We will leave all of the other settings untouched.

Each voice provider offers a host of settings you can modulate to customize voices. Here we will leave all the defaults alone.

Get a Phone Number

Now that we’ve configured how our assistant will behave, we want to figure out how to call it. We will need a phone number that we can make phone calls to.

There are 2 ways we can get a phone number into our Vapi account:

1. Purchase a Number Through Vapi: we can directly purchase phone numbers through Vapi.

   • Vapi will provision the phone number for us via Twilio
   • This can be done in the dashboard, or via the API (we will use the dashboard)

2. Import from Twilio or Vonage: if we already have a phone number with an external telephony provider (like Twilio or Vonage), we can import them into our Vapi account.

Provision via Vapi (faster)

The quickest way to secure a phone number for your assistant is to purchase a phone number directly through Vapi.

Ensure you have a card on file that Vapi can bill before proceeding, you can add your billing information in your dashboard at dashboard.vapi.ai/billing

Navigate to the “Phone Numbers” section & click the “Buy number” button:

Make sure you are in the 'Phone Numbers' dashboard tab.

We will use the area code 415 for our phone number (these are area codes domestic to the US & Canada).

Choose an area code for your phone number.

Currently, only US & Canada phone numbers can be directly purchased through Vapi. Phone numbers in other regions must be imported, see our phone calling guide.

Click “Buy”, after purchasing a phone number you should see something like this:

Here we can attach an assistant to the number for inbound calls (or perform an outbound call, with a select assistant).

The phone number is now ready to be used (either for inbound or outbound calling).

Import from Twilio or Vonage

We can also import an existing phone number we already own with either Twilio or Vonage.

For example’s sake, we will proceed with Twilio (though the steps are the same for Vonage as well).

Buy a Phone Number via Twilio (optional)

If you don’t already have a number in Twilio, you can purchase one by going to your Twilio console’s “Buy a number” section:

The Twilio 'Buy a Number' page in the Twilio console.

Once you’ve purchased a number, it will immediately be ready for import into Vapi.

Locate Twilio Account SID & Auth Token

To complete the import on Vapi’s side, we will need to grab our Twilio “Account SID” & “Auth Token”.

You should see a section for “API keys & tokens”, the credentials we will need for the import will live here.

We will want to navigate to the credentials section of our account.

Once we are in our “API keys & tokens” section, we will grab the Account SID & Auth Token:

We will use both of these credentials in the next step of importing via the Dashboard.

Import via Dashboard

Navigate to the “Phone Numbers” section & click the “Import” button:

Click 'Import' in the 'Phone Numbers' tab of your dashboard.

There you will input your phone number, as well as the credentials you retrieved in the previous step:

Hit “Import” & you will come to the phone number detail page:

The phone number detail page, we can configure our phone number here.

Your number is now ready to be attached to an assistant for inbound or outbound phone calling.

Attach Your Assistant

Now that we have a configured assistant & a phone number, we will put our assistant behind the phone number to pick up incoming phone calls.

In the Inbound area of the phone number detail view, select your assistant in the dropdown under Assistant.

Your assistant will now pick-up calls made to this phone number.

Call the Number

You can now make a phone call to the number. Your assistant will pick up the phone & manage the order-taking conversation. Happy ordering!

Your assistant won’t yet be able to hang-up the phone at the end of the call. We will learn more about configuring call end behaviour in later guides.