Click-to-Call via API

Connect my tools3 min readUpdated 2026-03-12

Click-to-Call via API

The click-to-call endpoint lets you initiate an outbound call directly from your own application. JustCall rings your agent first, then connects them to the customer — so the experience feels seamless to both parties.

Endpoint

POST https://api.justcall.io/v2/calls/make

Request Parameters

Parameter	Type	Required	Description
`from`	string	Yes	JustCall phone number to dial from (E.164 format)
`to`	string	Yes	Customer phone number to call (E.164 format)
`agent_id`	integer	No	ID of the agent who will handle the call. Defaults to the number owner.
`callback_url`	string	No	URL to receive real-time call status updates via POST
`caller_id`	string	No	Override the displayed caller ID (must be a verified number)

Code Example

curl -X POST "https://api.justcall.io/v2/calls/make" \
  -H "Authorization: {api_key}:{api_secret}" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "+14155551234",
    "to": "+14155559876",
    "agent_id": 42,
    "callback_url": "https://yourapp.com/webhooks/call-status"
  }'

Successful Response

{
  "status": "success",
  "message": "Call initiated",
  "data": {
    "call_id": "call_8f3a2b1c",
    "from": "+14155551234",
    "to": "+14155559876",
    "agent_id": 42,
    "direction": "outbound",
    "status": "ringing"
  }
}

Callback URL Payloads

If you provide a callback_url, JustCall sends a POST request at each stage of the call:

Status	Description
`ringing`	The agent's device is ringing
`in-progress`	Agent and customer are connected
`completed`	Call ended normally
`no-answer`	Customer did not pick up
`busy`	Customer line was busy
`failed`	Call could not be connected

Each callback includes call_id, status, duration (in seconds), and timestamp.

How the Call Flow Works

Your application sends the POST request.
JustCall rings the assigned agent (phone, desktop app, or mobile app).
When the agent answers, JustCall dials the customer number.
Both parties are connected. The call is logged automatically.
Status updates are sent to your callback URL in real time.

Common Use Cases

CRM click-to-call buttons — Let reps dial prospects without leaving Salesforce, HubSpot, or your custom CRM.
Automated outreach triggers — Fire a call when a lead fills out a high-intent form.
Support ticket callbacks — Trigger a return call when a ticket reaches a certain priority.

Error Handling

Code	Meaning	Fix
400	Missing required field (`from` or `to`)	Include both numbers in E.164 format
401	Invalid credentials	Check your API key and secret
404	`from` number not found in your account	Use a number assigned to your JustCall account
429	Rate limit exceeded	Wait and retry with exponential backoff