The code in the [HttpGet] section specifies that the route will return a task that will return an action result. The code in the [Route("/")] section specifies that the task will return an object that has a method named Ok(). The code in the [IActionResult] section specifies that the action result will be the return value of the Get method.
Shortcut: cag
[HttpGet]
[Route("/")]
public async Task<IActionResult> Get([FromQuery] Guid id)
{
return Ok();
}