// web.php
Route::get('foo', 'FooController@index')->middleware('json');

// or
Route::middleware('json')->group(function () {
    Route::get('foo', 'FooController@index');
    Route::get('bar', 'BarController@index');
})

// app/Http/Kernel.php
    ...

    protected $middlewareGroups = [
        ...
        'api' => [
            // Add it here
            'json',
            'throttle:60,1',
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],
        ...
    ];
    ...