I'm not much for assessment, especially with very young children. I think that we can learn a lot about children by being careful observers and facilitators in their work.
That said, this rubric from Play England, via playscapes, helps people who are designing play spaces to think about how they will be used by children. It promotes thinking that makes each play space unique to its environment and the people who will be using it, encouraging collaborative planning among people rather than a flip through a catalog to find something within budget.
The 10 design principles that the rubric is based on are all about personalization and individuality and inclusion. Reading through them makes me think that these principles are not only a good way to think about outdoor play, but indoor work spaces as well.