-These URIs are concatenated with the current message's
-Message-Id in `notmuch-show-stash-mlarchive-link'."
+This list is used for generating a Mailing List Archive reference
+URI with the current message's Message-Id in
+`notmuch-show-stash-mlarchive-link'.
+
+If the cdr of the alist element is not a function, the cdr is
+expected to contain a URI that is concatenated with the current
+message's Message-Id to create a ML archive reference URI.
+
+If the cdr is a function, the function is called with the
+Message-Id as the argument, and the function is expected to
+return the ML archive reference URI."