If JavaDoc doesn't recognize a tag, chances are that the tag is simply misspelled. Perhaps to be more helpful when a camelCased tag, such as @docRoot or @inheritDoc, is misspelled, JavaDoc introduced the following case check (JDK-4524350):

    ... is an unknown tag -- same as a known tag except for case

Although helpful, a bit more code could be *much* more helpful. Typically, misspelling is not about the letter case. It's about missing, extra or transposed characters. Here are some examples from bug fixes over the years: @params, @parm, @returns, @throw, @inherotDoc [sic].

JavaDoc could detect those and the camelCase misspellings using a string similarity metric, which other systems use in similar circumstances. For example:

% git rebace
git: 'rebace' is not a git command. See 'git --help'.

The most similar command is
rebase