Error using POST in Laravel API

I'm learning how to build an API using Laravel 5.4. *.

No Api.php :

$this->get('products', 'API\ProductController@index', ['except' => [
    'create', 'edit'
]]);

No Product.php :

class Product extends Model
{
    protected $fillable = ['name', 'description'];
}

No ProductController.php :

private $product;

public function __construct(Product $product)
{
    $this->product = $product;
}

public function index()
{
    $products = $this->product->all();

    return response()->json(['data' => $products]);
}

public function store(Request $request)
{
    return response()->json([
        'result' => $this->product->create($request->all())
    ]);
}

I reviewed my code and could not find any errors.

When I use GET it returns the products registered, however when I use POST I get this error:

What can it be?