Discoverability can be configured in zsh as part of completion system. I've found that this covers many of my needs:

    % grep -<TAB><TAB>

    --after-context        -A           # specify lines of trailing context
    --basic-regexp         -G           # use basic regular expression
    --before-context       -B           # specify lines of leading context
    --binary-files                      # specify type to assume for binary files
    --byte-offset          -b           # print the byte offset with output line
    --colour               --color      # distinguish matching string
    (...)