Discord.Net/src/Discord.Net.Commands/CommandError.cs

namespace Discord.Commands
{
    public enum CommandError
    {
        //Search
        UnknownCommand = 1,

        //Parse
        ParseFailed,
        BadArgCount,

        //Parse (Type Reader)
        //CastFailed,
        ObjectNotFound,
        MultipleMatches,

        //Preconditions
        UnmetPrecondition,

        //Execute
        Exception
    }
}