Template Tag Modifiers Not Being Parsed

I’m working on updating my Flickr for EE add-on to work with EE2. Within the fieldtype I have a main replace_tag() function, then several template tag modifiers; replace_title(), replace_link() and replace_description(). The main template tag gets parsed correctly and outputs what I expect it to. But the template tag modifiers don’t get parsed. When I include them in a template the tag itself gets spit back out.

I’ve tried making the tag as basic as possible to test:

function replace_link($data, $params = array(), $tagdata = FALSE) {
        
        return 'Test';
    }

But even that returns

{my_field:link}

Has anyone else had problems with template tag modifiers?

[Mod Edit: Moved to the Custom Field API Development forum]