I believe the format for the screenplay of an animated movie is virtually identical to a screenplay for a live action movie.
You need to break down the story into scenes, and the scenes into suggested shots (close-ups, establishing shots, point-of-view, etc.). Then you have to have the dialogue for each character, as well as anything like voice-over narration.
Notice that I used the word "suggested shot." Movies are a collaborative process, and the screenplay is only one component. The director (and, in a live-action movie, the cinematographer and the production designer) will interpret - and many times change - the script.
As for character descriptions, the screenplay should indicate some idea of what the character looks like. THAT job, however, falls to the individual animators. A detailed description is likely to be appreciated when the screenplay is being marketed to different studios or directors. But, again, you have to realize that other people will have their hands on the script, and will be adding their vision to your vision.
In ideal cases, all those visions complement and enhance each other. More often, the results are a mess.
Good luck!
You need to break down the story into scenes, and the scenes into suggested shots (close-ups, establishing shots, point-of-view, etc.). Then you have to have the dialogue for each character, as well as anything like voice-over narration.
Notice that I used the word "suggested shot." Movies are a collaborative process, and the screenplay is only one component. The director (and, in a live-action movie, the cinematographer and the production designer) will interpret - and many times change - the script.
As for character descriptions, the screenplay should indicate some idea of what the character looks like. THAT job, however, falls to the individual animators. A detailed description is likely to be appreciated when the screenplay is being marketed to different studios or directors. But, again, you have to realize that other people will have their hands on the script, and will be adding their vision to your vision.
In ideal cases, all those visions complement and enhance each other. More often, the results are a mess.
Good luck!