Outbound calls

Voiceflow supports outbound calling using Twilio, allowing your agent to initiate a call to any number via API. This is useful for automating voice actions - such as welcome calls, reminders, or follow-ups - triggered from tools like Zapier or your own scripts.

⚠️

Comply with your local regulations regarding automated calls

In many regions, it is a violation of law to create automated outbound calls without consent. This may lead to your Twilio number or account being suspended and potentially incur fines. You are solely responsible for ensuring compliance with all relevant regulations.

• Twilio Phone Number Regulations
• Twilio Voice Guidelines

ℹ️

Outbound calling is currently in alpha

Outbound calls are currently in alpha and the API endpoint, /v1alpha1/ may be subject to change during development.

How it works

To trigger an outbound call, your app must make a POST request to a Voiceflow API endpoint associated with your agent. You can find this endpoint by navigating to Interfaces > Telephony > View Outbound API. Each agent has a unique API URL based on its internal ID.

The API is shown in a curl format. It must include an Authorization header with the associated API Key of the agent. This can be found under Interfaces > API keys.

API reference

Endpoint

POST https://runtime-api.voiceflow.com/v1alpha1/phone-number/<AGENT_ID>/outbound

Headers

Body

{
  "to": "+15551234567",
  "variables": {
    "user_name": "Jane",
    "account_type": "Premium"
  }
}

• to: The phone number to call (E.164 format).
• variables: Optional. A JSON object with any Voiceflow variables to inject at launch.

Concurrency limits

Outbound calls share the same concurrency pool as inbound calls. The number of simultaneous calls you can make is determined by your plan limits.

Troubleshooting

500 Internal Server Error

If you're seeing a 500 error, your Twilio number may not have outbound permissions for the region you're calling. Make sure the region is enabled in your Twilio geo-permissions dashboard.