Как то так. Добавьте все содержимое в список строк, а затем выведите его в файл.
List<string> tools = new List<string>()
{
"Hammer", "Wrench", "Screwdriver", "etc"
};
List<string> output = new List<string>();
int count = 1;
foreach ( string toolName in tools )
{
if (output.Count == 61)
{
output.Add ( "some string" );
count++;
continue;
}
output.Add ( "[\"at" + count.ToString ( "D4" ) + "\"] = < " );
output.Add ( "[\"at" + count.ToString ( "D4" ) + "\"] = < " );
output.Add ( "text = < \"" + toolName + "\" >" );
output.Add ( "description = <\" * \">" );
output.Add ( ">" );
count++;
}
string path = @"C:\output.txt";
File.WriteAllLines ( path , output.ToArray ( ) );