In case you need to use the macro on URLs pointing to the Confluence instance, you should use the tiny URLs. Otherwise (usually) the Confluence built-in autoconverter will take priority in converting the link.

You can determine the tiny URL easily by typing 'k' in the view mode of a page.

Labels may be determined correctly (i.e. will show the title of the page) even if the page needs authentication to be accessed. See Authentication for details.