Apple - Is there a good command-line ID3 tool for OS X?

If you have Homebrew installed (highly recommended), you can just do:

brew install id3lib

This installs several id3 command-line tools, including id3tag, id3convert, id3cp and id3info. No need for python or perl scripting; just use regular shell commands.

Usage: id3tag [OPTIONS]... [FILES]...
   -h         --help            Print help and exit
   -V         --version         Print version and exit
   -1         --v1tag           Render only the id3v1 tag (default=off)
   -2         --v2tag           Render only the id3v2 tag (default=off)
   -aSTRING   --artist=STRING   Set the artist information
   -ASTRING   --album=STRING    Set the album title information
   -sSTRING   --song=STRING     Set the title information
   -cSTRING   --comment=STRING  Set the comment information
   -CSTRING   --desc=STRING     Set the comment description
   -ySTRING   --year=STRING     Set the year
   -tSTRING   --track=STRING    Set the track number
   -TSTRING   --total=STRING    Set the total number of tracks
   -gSHORT    --genre=SHORT     Set the genre
   -w         --warning         Turn on warnings (for debugging) (default=off)
   -n         --notice          Turn on notices (for debugging) (default=off)

There's an OS X compatible version of the id3lib library available here on GitHub. It claims to support both ID3v1 and ID3v2.

The python module Mutagen is shipped with the command-line ID3 tool named mid3v2 replacement for id3lib's.
From the usage documentation :

You can set the value for any ID3v2 frame by using '--' and then a frame ID.
For example:
mid3v2 --TIT3 "Monkey!" file.mp3 would set the "Subtitle/Description" frame to "Monkey!".