WordPress at a glance
filter is not described

category_description filter-hook . WP 1.2.0

Filters the category description for display.

Usage

add_filter( 'category_description', 'filter_function_name_1987', 10, 2 );
function filter_function_name_1987( $description, $category ){
	// filter...

	return $description;
}
$description(string)
Category description.
$category(object)
Category object.

Where the hook is called

Walker_Category::start_el()
wp-includes/class-walker-category.php 116
$link .= 'title="' . esc_attr( strip_tags( apply_filters( 'category_description', $category->description, $category ) ) ) . '"';

Where the hook is used (in WP core)

Does not used.