How to enable all Tag Descriptions in loop?

Modified from the get_tags() Codex Example

$tags = get_the_tags(); // for the specific post
// $tags = get_tags(); // all tags
$html="<div class="post_tags">";
foreach ( $tags as $tag )
{
    $tag_link = get_tag_link( $tag->term_id );

    $html .= "Describtion for ".ucfirst( strtolower( $tag->name ) ).": $tag->description";
    $html .= "<a href="https://wordpress.stackexchange.com/questions/21234/{$tag_link}" title="{$tag->name} Tag" class="{$tag->slug}">{$tag->name}</a>";
    }

$html .= '</div>';
echo $html;