git tag -a HEAD leads to ambiguous branch name

Good evening, today I encountered a warning using  git version 2.39.0.windows.2: /warning: refname 'HEAD' is ambiguous./ It turned out, having written /git tag -a HEAD -m "Some message."/ was the culprit. As /git branch HEAD/ yields the following error /fatal: 'HEAD' is not a valid branch name/ I wanted to aks, whether a similar check should  be applied to tag names. Best regards Johannes Wilde