creating shortcode to pull json array

As per documentation on wp_remote_get() it doesn’t return you just the body of requested resource. Its return will be either the array of data or WP_Error object on failure.

The simplest snippet to get to the body would be:

$json = wp_remote_retrieve_body( wp_remote_get( $url ) );

PS it’s kinda weird to be doing this in shortocde, are you sure it’s most appropriate place for it? 🙂