The API Trigger is a POST request, which requires an [API Key](../configurations/api-keys). It expects a valid JSON with `phone_number` and `initial_context`.
`initial_context` is a valid JSON object, which contains any contextual information that you would want your voice agent to access. You can refer to these values in your prompts using **Handle Bars**, which are values enclosed in `{{` and `}}`.
Example: If you have below JSON as your `initial_context`
```
{
"initial_context": {
"user": {
"name": "John"
}
}
}
```
you can refer to the user name in your prompts as `{{initial_context.user.name}}`.
