SIP introduction

Create an assistant

Create an assistant with the POST /assistant endpoint. This is the same as creating an assistant for any other transport.

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{
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  "name": "My SIP Assistant",
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  "firstMessage": "Hello {{first_name}}, you've reached me over SIP."
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}

Create a SIP phone number

Create a SIP phone number with the POST /phone-number endpoint.

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{
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  "provider": "vapi",
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  "sipUri": "sip:your_unique_user_name@sip.vapi.ai",
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  "assistantId": "your_assistant_id"
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}

Start a SIP call

Use any SIP softphone (e.g., Zoiper, Linphone) to dial your SIP URI (e.g., sip:your_unique_user_name@sip.vapi.ai).

The assistant will answer your call. No authentication or SIP registration is required.

Send SIP headers to fill template variables

To fill template variables, send custom SIP headers with your call.

For example, to fill the first_name variable, send a SIP header:

x-first_name: John

Header names are case-insensitive (e.g., X-First_Name, x-first_name, and X-FIRST_NAME all work).

Use a custom assistant for each call

You can use a custom assistant for SIP calls just like for phone calls.

Set the assistantId to null and the serverUrl to your server, which will respond to the assistant-request event.

PATCH /phone-number/:id

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{
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  "assistantId": null,
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  "serverUrl": "https://your_server_url"
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}

Now, every time you make a call to this phone number, your server will receive an assistant-request event.