functions.php

/*
* 
* NOT YET IMPLEMENTED FUNCTIONALITY!! EEEEEEP!!!!
* 
* Taken from ticket: #16784
* https://core.trac.wordpress.org/attachment/ticket/16784/16784.diff
* 
* NOT YET IMPLEMENTED FUNCTIONALITY!! EEEEEEP!!!!
* 
* 
* Display or retrieve description for a post type archive. 
* 
* This is optimized for archive.php and archive-{$post_type}.php template files 
* for displaying the description of the post type. 
* 
* @since 4.4.0 
* 
* @param bool $display Optional, default is true. Whether to display or retrieve description. 
* @return string|null Description when retrieving, null when displaying or failure. 
*/ 
function post_type_archive_description( $display = true ) { 
	if ( ! is_post_type_archive() ) { 
		return; 
	} 

	$post_type = get_query_var( 'post_type' ); 
	if ( is_array( $post_type ) ) { 
		$post_type = reset( $post_type ); 
	} 

	$post_type_obj = get_post_type_object( $post_type ); 

	/** 
	* Filter the post type archive description. 
	* 
	* @since 4.4.0 
	* 
	* @param string $post_type_description Post type 'description' argument. 
	* @param string $post_type             Post type. 
	*/ 
	$description = apply_filters( 'post_type_archive_description', $post_type_obj->description, $post_type ); 

	if ( $display ) { 
		echo $description; 
	} else { 
		return $description; 
	} 
} 
	 
/*
* 
* Taken from old open ticket: #34656
* https://core.trac.wordpress.org/attachment/ticket/34656/34656.diff
* 
* This may not work forever, if these tickets are implemented into core.
* ¡¡ Be aware !!
* 
*/


function tip_get_the_archive_description() { 

	$description = ''; 

	if ( is_post_type_archive() ) { 
	        $description = post_type_archive_description( '', false ); 
	} else { 
	        $description = term_description(); 
	}

	return $description;

 }
add_action( 'get_the_archive_description', 'tip_get_the_archive_description' );

The idea of this function / filter is to display the description given when registering a custom post type on the archives.php page by default using the standard the_archive_description().