I think credits are always appreciated especially if you make use of special scripts - or any other resource - made by any OFPEC members (eg. "Mando chase" script from Mandoble, "Isbodyhidden" script from Snypir etc.); generally speaking, when you show a person's name on credits, you pay homage to him for something he created and which you make use in your mission. My personal thought is showing credits is a moral duty because noone should take the authorship of something he didn't create.
Making resource via description.ext in order to show credits is just one of many ways to put credits. If it is too technically difficult for you to make that, then you can give credits inside a "readme.txt" file attached to mission.