For simple JSON encoding any solidity related type should have [FromJSON](http://hackage.haskell.org/package/aeson-1.4.1.0/docs/Data-Aeson.html#t:FromJSON) and [ToJSON](http://hackage.haskell.org/package/aeson-1.4.1.0/docs/Data-Aeson.html#t:ToJSON) instances. In first view `UIntN` type have no. Solidity primitive type check list: - [ ] Address - [ ] Bool - [ ] Bytes - [ ] BytesN - [x] IntN - [x] UIntN - [ ] List - [ ] ListN - [ ] String - [ ] Tuple - [ ] OneTuple