> ## Documentation Index
> Fetch the complete documentation index at: https://docs-sms.mifumolabs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Contact Opt-In

Opt a contact back in to receive messages.

<ParamField path="contact_id" type="string" required>
  Contact ID
</ParamField>

## Success Response (200)

<ResponseField name="success" type="boolean">
  Operation success status
</ResponseField>

<ResponseField name="message" type="string">
  Success message
</ResponseField>

<ResponseField name="opt_in_at" type="string">
  Timestamp of opt-in
</ResponseField>

<ResponseExample>
  ```json theme={null}
  {
    "success": true,
    "message": "Contact opted in successfully",
    "opt_in_at": "2025-11-27T10:30:00Z"
  }
  ```
</ResponseExample>