Retell AI callback from a contact form

What it is

This n8n workflow phones people back as soon as they send your contact form. The form asks for a name, an email, a phone number and a subject. One HTTP request then asks Retell AI to dial that number from your Retell number, with your voice agent on the line. The agent gets the four answers as variables for its script. Two nodes make it up.

Who it suits

Small businesses and agencies that want every enquiry answered by voice, and that have built a voice agent in Retell or will build one. Skip it if you have no agent yet. The file only starts the call. The conversation lives in Retell.

You need a little n8n and a Retell account with a phone number and an agent. Its author puts setup at about 5 minutes, which assumes the agent already exists.

Where to use it

Any n8n that can reach Retell’s API. The form has its own address, so a site’s contact button can link straight to it.

• n8n Cloud: import the file into a new workflow there
• Your own n8n server: the same file and steps
• Your website: link the contact button to the form’s production address
• Retell: the call and its transcript show in your Retell call history

Setup

Get it saves a zip with workflow.json and Mindket’s setup notes in your downloads folder. Have the Retell number and the agent ready first.

1. In n8n, create a workflow, open its menu, choose Import from File and pick workflow.json.
2. In HTTP Request, replace <YOUR_RETELL_KEY> in the Authorization header with your Retell API key. The brackets go too, so the header reads Bearer, a space and the key.
3. In the JSON body of the same node, put your Retell number in place of YOUR_RETELL_NUMBER, with its plus and country code, and your agent’s ID in place of YOUR_AGENT_ID.
4. In your agent’s prompt in Retell, write {{name}}, {{email}} and {{subject}} where the caller’s details belong.
5. Save, open the form’s test address and send it with your own phone number.
6. Press Publish, then link your contact button to the form’s production address.

How to use it

Visitors fill in the form and press Get a Call. n8n passes their details to Retell straight away, and Retell dials the number they typed. The form shows its thank-you line at once. What the agent says, and what happens after the call, is set in Retell.

Example

Someone sends the form with these answers.

Name: Jordan Price
Email: jordan@example.com
Phone Number: +14155550123
Subject: A quote for a kitchen leak

n8n posts the caller’s number, your Retell number, your agent’s ID and these four values to Retell, and a moment later the phone rings. Your agent can open with a line like this one, written in Retell:

Hi {{name}}, thanks for your message about {{subject}}. Do you have two minutes?

Retell answers the request with the call’s ID and status, which you can read in the run under Executions.

For newcomers and experts

If you are new. n8n draws a workflow as boxes joined by lines, and each box, a node, does one job. This one has two: the form and the call. Test with your own number first. Then open HTTP Request under Executions to read Retell’s answer, where a wrong key or a badly written number shows up.

For experts. The request goes to Retell’s create-phone-call endpoint, with a JSON body that n8n fills from the form.

POST https://api.retellai.com/v2/create-phone-call

Every value goes into the body as typed. A double quote in the subject breaks the JSON. None of the form’s fields is required, so an empty phone number reaches Retell and fails there.

Good to know

Each form costs a call, and an open form can dial any number.

• Billing: Retell bills the call’s minutes, and a number bought there has its own monthly fee
• Open form: anyone with the form’s address can type any number, and your Retell account will call it. Turn on the form trigger’s basic authentication, or check numbers before the call
• Calling rules: many countries require consent before an automated or AI voice call. Say on the form that you will phone back, and check the rules where your callers live
• Number format: Retell expects numbers with a plus and a country code. The form takes free text, so ask for that format in the field’s placeholder
• One variable’s name: the body calls it phone number, with a space. If your agent never fills it in, rename it phone_number in the body and the prompt
• Where the data goes: the four answers go to Retell, and the call’s audio and transcript stay there
• Your key: it sits in a header, so take it out before you share the workflow
• Credentials: the JSON holds none