wp api custom endpoint

// Register a REST route
add_action( 'rest_api_init', function () {
    //Path to meta query route
    register_rest_route( 'boardgame/v2', '/fedrated_query/', array(
            'methods' => 'GET', 
            'callback' => 'custom_meta_query' 
    ) );
});

// Do the actual query and return the data
function custom_meta_query(){
    if(isset($_GET['query'])) {
        $query = $_GET['query'];
        // Set the arguments based on our get parameters
        $args = Array(
                    'post_type' => 'post',
                    'posts_per_page' => 100,
                    'meta_query' => array(
                                    'relation' => 'OR',
                                    array(
                                        'key' => 'etitle',
                                        'value' => $query,
                                        'compare' => 'LIKE'
                                    ),
                                  )
                );
        // $args = array (
        //     array(
        //         'meta_key' => 'etitle',
        //         'meta_value' => 'catan',
        //         'meta_compare' => 'LIKE',
        //     ),
        //     // array(
        //     //     'key' => $query[0]['key'],
        //     //     'value' => $query[0]['value'],
        //     //     'compare' => '=',
        //     // ),
        // );
        // Run a custom query
        $meta_query = new WP_Query($args);
        if($meta_query->have_posts()) {
            //Define and empty array
            $data = array();
            // Store each post's title in the array
            while($meta_query->have_posts()) {
                $meta_query->the_post();
                $data[] =  get_the_title();
            }
            // Return the data
            return $data;
        } else {
            // If there is no post
            return [];
        }
    }
}