Add custom post type to Jetpack

gistfile1.php

function tweakjp_allow_cpt( $allowed_post_types ) {
    // my_cpt is the name of your <span class="hilite">Custom</span> <span class="hilite">Post</span> <span class="hilite">Type</span>
    $allowed_post_types[] = 'my_cpt';
    return $allowed_post_types;
}
add_filter( 'rest_api_allowed_post_types', 'tweakjp_allow_cpt' );