Is "The Open Window" a narrative or descriptive story?
To be perfectly honest, I had never seen the term "descriptive story" until I read your question. I did a Google search and found many "hits," but I still do not understand this term.
What I do know is that a narrative is a story that tells a sequence of fictional or non-fictional events. Description is one of the tools that is used by writers of narratives; narrative writers, as part of their narratives, describe their characters and their settings.
"The Open Window," by H.H. Munro uses description, but it is most certainly a narrative. There is clearly a sequence of events that leads to a conclusion. I would have to conclude that "The Open Door" should be classified as a narrative.