To me, a cast list should provide information about how the character fits into the story and plot. Unfortunately, what I typically see in cast lists is - Character X is the 'add relationship' (i.e., friend, brother, sister, etc) of Character Y and a physical description of the character (e.g., 5'-3" tall 121 pounds, 36C-24-36, 36 years old, long blond hair, blue eyes, very cute).
If I don't remember Character X and their part in the story, then the description is meaningless; all I have is a mental image of what the character Y looks like.
Then there are the stories that provide an updated cast list of 20+ characters at the start of every chapter and I have to follow the links to characters to figure out how the character is related to the overall cast. For example: A is a friend of B, B is a cousin of C, C is the roommate of D, D is the MC's brother.