Another challenge is to elicit a criterion because beyond the word level, a student has many options when producing spoken language. That is to say, that when designing a task we must try to be as specific with the micro- or macro-skills we are setting for the activity as we can, so you will be sure which aim you want your students to achieve. All of this bearing in mind that no speaking task is able to separate the only skill of oral production, since most of them involve the interaction of aural comprehension. Now, in order to conclude this post, I want to share with my colleagues these useful webpages I've found where you can design rubrics, which I consider as a great tool when being objective is the principal aim. Rubrics, are more than a check list and they provide corrective feedback. Take your time to explore and try them.
Hope you find this post useful for your teacing process.