grammar - Grammatical name/function of "what" in the following sentence

I came across this sentence fragment among the instructions for a writing lab report: "Simply describe what the data that you collected."

I feel like it should have an "are" at the end (minimally completing the sentence), or better, shouldn't have the "what" in the sentence.

How would you diagram that sentence if it read, "Simply describe what the data that you collected are."?

My best guess is the following:

• (You) -- implicit subject


• describe -- verb


• what the data that you collected are -- relative clause
  
  
  
  • what -- relative pronoun of relative clause
  
  
  
  • data -- subject of relative clause
  
  
  • are -- verb of relative clause
  
  
  • that you collected -- embedded relative clause
    
    
    
    • that -- relative pronoun of embedded relative clause
    
    
    • you -- subject of embedded relative clause
    
    
    • collected -- verb of embedded relative clause