Custom webhooks

Custom webhooks give developers full control over the hyzl integration layer. You can trigger calls with an HTTP POST. You can also receive call results at any endpoint you specify. hyzl carries them as two cards on the Integrations page. They are Custom inbound webhook and Custom outbound webhook.

Custom webhooks are intended for developers and technical users. If you would prefer a no-code solution, use Zapier Inbound to trigger calls and Zapier Outbound to receive results instead.

Webhooks require an active AI Calling subscription. If your subscription lapses, hyzl pauses your existing webhooks automatically. They resume when you resubscribe. If you create a new webhook without an active subscription, the request returns HTTP 402.

Inbound webhooks: trigger a call

Inbound webhooks let external systems trigger AI calls on-demand. When your customer relationship manager (CRM) sends a request to your inbound webhook URL, hyzl starts a call automatically. Any other system can send the same request.

Set up an inbound webhook

Go to Integrations
Find the Custom inbound webhook card and click View integration
Click Create inbound webhook
Click Create Campaign to set up the AI script
Write your prompt
Test the prompt
Use the webhook URL to trigger calls from your CRM

The + Custom integration menu in the page header runs the same flow, under Custom inbound webhook. hyzl creates the webhook with a unique slug as soon as you click Create inbound webhook.

Endpoint

POST https://wh.atll.as/{your-webhook-slug}

hyzl binds each inbound webhook to one campaign when you create it. You do not need to name the campaign in each request.

Request body

{
  "type": "calls.execute",
  "data": {
    "phoneNumber": "+15551234567",
    "firstName": "Jane",
    "lastName": "Smith",
    "email": "jane@example.com",
    "companyName": "Acme Corp",
    "note": "Expressed interest in the enterprise plan"
  }
}

Field	Required	Description
`type`	Yes	Must be `"calls.execute"`
`data.phoneNumber`	Yes	E.164 format recommended (`+15551234567`)
`data.firstName`	No	Used for personalization
`data.lastName`	No
`data.email`	No	Used for email follow-ups if configured
`data.companyName`	No
`data.note`	No	Additional context for this contact
`data.address1`, `data.address2`, `data.city`, `data.state`, `data.zipCode`	No	Address fields, available for personalization

Field names are camelCase. hyzl ignores snake_case names such as first_name and phone_number. It places the call with phoneNumber only.

Response

{ "success": true }

A 201 response means hyzl accepted the request. The campaign attached to the webhook must be active before hyzl places the call. If you are out of credits, hyzl records the call as cancelled and still returns the same response status.

Customize the phone call

The webhook is bound to an inbound campaign in AI Calling. That campaign owns every call setting, including voice, call script, voicemail message, and follow-ups. It also owns call forwarding, keypad navigation, language, and background ambiance. Whatever is on the campaign is what every webhook-triggered call uses. To change call behavior:

Open AI Calling
Find the campaign your webhook uses. hyzl labels it as inbound.
Edit any setting: voice, script, follow-ups, voicemail, etc.
Save

Inbound campaigns can be edited at any time (unlike outbound campaigns, which lock once they start dialing). Changes apply to all future calls triggered by the webhook. Already-completed calls keep the settings they ran with.

View results

Every call triggered by the webhook appears in the bound campaign’s results table in AI Calling. That is the same place outbound campaign results live. Each call result includes the transcript, recording, AI summary, lead warmth classification, and extracted action items. See Call Results & Transcripts for what is in the detail panel. You can also get each completed call at your own endpoint as it happens. To do that, configure a Response Webhook on the inbound webhook. The section below covers it. hyzl POSTs the result back to your URL when the call ends.

Outbound webhooks: receive call results

Outbound webhooks broadcast every call completion event to your configured endpoint(s). Whenever a call finishes, hyzl POSTs the results to every outbound webhook URL you have configured. The call can come from a manual campaign, an inbound webhook trigger, or a test call.

Creating an outbound webhook manually is only for custom webhooks. If you want to send call results to Zapier, set up an outbound Zapier integration instead. hyzl creates its outbound webhook automatically and labels it Managed by zapier.

Set up an outbound webhook

Go to Integrations
Find the Custom outbound webhook card and click View integration
Click Create outbound webhook
Enter your endpoint URL
Choose the HTTP method (POST or GET)
Add custom headers for authentication if you need them (see Custom Headers)
Click Create Webhook to save it
Click the Test button on the webhook’s card to check connectivity

The + Custom integration menu in the page header runs the same flow, under Custom outbound webhook.

Event

Outbound webhooks emit a single event:

Event	When
`call.finished`	Fires after the call completes and final analysis is attached (transcript, summary, lead warmth)

Payload

{
  "type": "call.finished",
  "timestamp": 1730179200000,
  "webhook": {
    "id": "webhook_abc123",
    "type": "outbound"
  },
  "call": {
    "id": "call_xyz789",
    "status": "finished",
    "recipient": {
      "phoneNumber": "+15551234567",
      "firstName": "Jane",
      "lastName": "Smith",
      "email": "jane@example.com",
      "address1": "123 Main St",
      "city": "Austin",
      "state": "TX",
      "zipCode": "78701",
      "note": "VIP lead"
    },
    "summary": "Jane expressed interest in the enterprise plan and asked about pricing.",
    "transcript": [
      {
        "who": "assistant",
        "what": "Hi, is this Jane?",
        "when": "2024-04-30T14:00:03.000Z"
      },
      {
        "who": "user",
        "what": "Yes, speaking.",
        "when": "2024-04-30T14:00:05.000Z"
      }
    ],
    "recording": "https://...",
    "duration": 142000,
    "analysis": {
      "sentiment": "positive",
      "lead_warmth": "hot",
      "justification": "Expressed immediate interest and asked specific pricing questions."
    },
    "tokensConsumed": 1
  },
  "campaign": {
    "id": "campaign_123",
    "name": "Q4 Outreach"
  }
}

Field reference

Path	Description
`type`	Always `"call.finished"`
`timestamp`	Unix epoch in milliseconds
`webhook.id`	The outbound webhook’s ID
`webhook.type`	Always `"outbound"`
`call.id`	The call ID
`call.status`	One of: `finished`, `missed`, `failed`
`call.recipient.phoneNumber`	Contact phone in E.164
`call.recipient.firstName` / `lastName` / `email`	Contact identity fields
`call.recipient.address1` / `address2` / `city` / `state` / `zipCode` / `note`	Optional address + note
`call.summary`	One-paragraph AI summary
`call.transcript`	Array of conversation turns. `who` is typically `"user"` (caller) or `"assistant"` (AI), and `when` is an ISO timestamp. Each turn is `{ who, what, when }`
`call.recording`	URL to the MP3 recording
`call.duration`	Call length in milliseconds
`call.analysis.sentiment`	`positive`, `neutral`, or `negative`
`call.analysis.lead_warmth`	`hot`, `warm`, `cold`, `dead`, or `unknown`
`call.analysis.justification`	AI’s reasoning for the warmth classification
`call.tokensConsumed`	Credits used for the call
`campaign.id` / `campaign.name`	Source campaign info

Status values

Status	Meaning
`finished`	Call completed successfully
`missed`	The contact did not answer or went to voicemail
`failed`	Technical error occurred

Lead Warmth values

Value	Meaning
`hot`	High interest, ready to move forward
`warm`	Some interest, needs nurturing
`cold`	Low interest or not qualified
`dead`	No interest or wrong number
`unknown`	Unable to determine

Sentiment values

Value	Meaning
`positive`	Friendly, receptive conversation
`neutral`	Professional, factual interaction
`negative`	Frustrated or hostile

The call.recipient field names are camelCase (firstName, phoneNumber). It has no company field. Build your integrations against the names shown above.

Response webhooks

You configure a response webhook on an inbound webhook. It sends the call result back to one endpoint after an inbound-triggered call completes. This forms a request/response pattern.

Set up a response webhook

Click Webhook Settings on your inbound webhook
Scroll to Response Webhook (Optional)
Enter your callback URL
Add custom headers if you need them

The response webhook fires with type: "call.completed". Its payload has the same overall shape as the outbound webhook payload, with two differences. First, recipient, summary, transcript, recording, duration, analysis, and tokensConsumed are all optional. Some calls never connect, so they will not have all fields populated. Second, the webhook object carries the inbound webhook’s slug instead of type ({ "id": "...", "slug": "your-webhook-slug" }). Outbound webhooks use type: "call.finished", not call.completed.

Custom Headers

Custom headers let you authenticate against CRMs or other systems that require API keys or access tokens.

Add headers

Expand Custom Headers (Optional) while you create or edit a webhook
Click Add Header
Enter header name and value (e.g. Authorization, Bearer token123)

hyzl encrypts your headers at rest. The portal never shows them again after you save.

FollowUp Boss example

FollowUp Boss requires these headers:

X-System: your-app-name
X-System-Key: your-api-key
Authorization: Basic base64(api-key:)

Add them as:

X-System → atllas-integration
X-System-Key → your-followupboss-api-key
Authorization → Basic {base64-encoded-key}

HubSpot example

HubSpot workflow webhooks typically do not require custom headers. Just configure the webhook URL in your HubSpot workflow. For HubSpot API endpoints, add:

Authorization: Bearer your-access-token

Tests and logs

Test button

Each webhook has a Test button that sends a call.completed-shaped payload with example data:

{
  "type": "call.completed",
  "timestamp": 1730179200000,
  "webhook": { "id": "webhook_test_outbound_456", "type": "outbound" },
  "call": {
    "id": "call_test_abc123def456",
    "status": "finished",
    "recipient": {
      "phoneNumber": "+15555551234",
      "firstName": "Jessica",
      "lastName": "Smith",
      "email": "jessica.smith@example.com"
    },
    "summary": "Example call summary from the test button.",
    "transcript": [
      {
        "who": "assistant",
        "what": "Hi Jessica, this is Alex.",
        "when": "2024-04-30T14:00:03.000Z"
      },
      {
        "who": "user",
        "what": "I'm doing well, thanks for calling!",
        "when": "2024-04-30T14:00:05.000Z"
      }
    ],
    "recording": "https://storage.googleapis.com/atllas-call-recordings/test-recording-example.mp3",
    "duration": 123456,
    "analysis": {
      "sentiment": "positive",
      "lead_warmth": "hot",
      "justification": "Example justification."
    },
    "tokensConsumed": 42
  },
  "campaign": { "id": "campaign_test_xyz789", "name": "Example Campaign" }
}

The test validates:

The URL is reachable from our servers
Your custom headers are correct
Your endpoint responds with a 2xx status

Handle both event types before you rely on this in production. The test payload uses call.completed, and a real outbound webhook delivery uses call.finished. This matters when your endpoint routes behavior by event type.

Fix common problems

Webhook not firing

For inbound webhooks:

Check that you created the campaign (click Create Campaign)
Check the campaign has a prompt configured
Make sure you send the correct payload format (calls.execute)

For outbound webhooks:

Check the URL is correct and reachable
Use the Test button to check connectivity

Authentication errors

If receiving 401 or 403 errors:

Check custom headers are correct
Check that the API key has not expired
Test with a simple endpoint (such as webhook.site) first
Review the destination system’s authentication requirements

Call not triggering from inbound webhook

Make sure campaign status is not executing or completed
Check you have available calling credits. hyzl records an out-of-credit call as cancelled in the campaign’s results
Check the phone number is in correct format (+1...)

Security best practices

Keep webhook URLs secret. Treat them like API keys
Use HTTPS only. Never use HTTP endpoints
Rotate headers periodically. Update API keys regularly
Test in staging first. Use the Test button before production

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Integrations

Custom webhooks

Inbound webhooks: trigger a call

Set up an inbound webhook

Endpoint

Request body

Response

Customize the phone call

View results

Outbound webhooks: receive call results

Set up an outbound webhook

Event

Payload

Field reference

Status values

Lead Warmth values

Sentiment values

Response webhooks

Set up a response webhook

Custom Headers

Add headers

FollowUp Boss example

HubSpot example

Tests and logs

Test button

Fix common problems

Webhook not firing

Authentication errors

Call not triggering from inbound webhook

Security best practices

​Inbound webhooks: trigger a call

​Set up an inbound webhook

​Endpoint

​Request body

​Response

​Customize the phone call

​View results

​Outbound webhooks: receive call results

​Set up an outbound webhook

​Event

​Payload

​Field reference

​Status values

​Lead Warmth values

​Sentiment values

​Response webhooks

​Set up a response webhook

​Custom Headers

​Add headers

​FollowUp Boss example

​HubSpot example

​Tests and logs

​Test button

​Fix common problems

​Webhook not firing

​Authentication errors

​Call not triggering from inbound webhook

​Security best practices

Inbound webhooks: trigger a call

Set up an inbound webhook

Endpoint

Request body

Response

Customize the phone call

View results

Outbound webhooks: receive call results

Set up an outbound webhook

Event

Payload

Field reference

Status values

Lead Warmth values

Sentiment values

Response webhooks

Set up a response webhook

Custom Headers

Add headers

FollowUp Boss example

HubSpot example

Tests and logs

Test button

Fix common problems

Webhook not firing

Authentication errors

Call not triggering from inbound webhook

Security best practices