My controller is ignoring my custom validation rule - validation

Question

I need a custom validation rule for my application. As a proof of concept I created a simple validation rule. For testing purposes, the passes method returns false. I added the validation to my controller, but even though the validator returns false, the controller proceeds as though the validation succeeded. I used the debugger to confirm that the passes method is indeed being hit and is returning false.
Why am I doing wrong?
Here's my rule class:
namespace App\Rules;
use Illuminate\Contracts\Validation\Rule;
class UniqueAgent implements Rule
{
protected $id;
/**
* #return mixed
*/
public function getId()
{
return $this->id;
}
/**
* #param mixed $id
*/
public function setId($id): void
{
$this->id = $id;
}
/**
* UniqueAgent constructor.
*/
public function __construct($id)
{
$this->setId($id);
}
public function passes($attribute, $value)
{
// TODO: Implement passes() method.
return false;
}
public function message()
{
// TODO: Implement message() method.
}
}
Here's the controller code:
public function update(Request $request, $id)
{
// UniqueAgent rule returns 'false'
$validateData = $request->validate([
'agency' => [
'required',
new UniqueAgent($id)
]
]);
$agent = Agent::findOrFail($id)
$agent->agency = $request->input('agency');
$agent->save();
}
Thanks

Answer 1

Problem solved. For anyone interested, I hadn't added a return value to the message method of the UniqueAgent class. I added a return "some string" and now the controller redirects the client to view and displays the error message.
In my opinion, this is a poor design. If not returning a message string causes the class not to perform as intended, it shouldn't just fail quietly. In my opinion, it would be better for if the controller simply did what it does when the validation fails (i.e., redirects to the view), with or without an error message.