Custom Validation

Hi Laracasts, I'm building validation into my application right now. I'd like to add custom validation. I've added a service provider.

<?php

namespace Uma\Providers;

use Validator;
use Illuminate\Support\ServiceProvider;
use Uma\Services\ValidationService;

class ValidationServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        Validator::extend('foo', function($attribute, $value, $parameters) {
            return $value == 'foo';
        });
    }

    /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

I also added the provider to config/app.php.

Uma\Providers\ValidationServiceProvider::class,

And I've added my error message to resources/lang/en/validation.php.

"foo" => "Your input was invalid!",

Here is how I call validation in the controller.

$validator = Validator::make($request->all(), ['foo' => 'foo']);

But when I hit the site, it doesn't validate.

curl "http://domain.com/route?foo=bar"

This returns my data instead of a validation error. I've been following the custom validation rules section of the validation documentation. I also read up on service providers and I think I know how they work but they are still fairly new to me. Am I missing something?