+1, I'm impressed how far these prototypes can get you, especially if there's an extra layer of correctness on top of the existing Haskell type signatures. For instance, LiquidHaskell [1] can naturally shift you towards implementing most of the necessary validation and parsing logic as part of your work on precise type signatures.

[1] https://www.youtube.com/watch?v=zCJV0xNY06o