You can also link to external documentations via the tool option --comment.external_doc prefix=url.
All unique-names starting with prefix will be linked to the url.
If the url contains two dollar signs $$, they will be replaced by the unique-name.
By default the tool supports http://en.cppreference.com/w/ with a prefix of std:: by default.
You can override to a different URL by specifying
--comment.external_doc std::=new-url.