Writing is really simple.
Just call .toJson on your data:

      import ba.sake.tupson.{given, *}
      
      case class WriteData(
        bln: Boolean,
        int: Int,
        dbl: Double,
        str: String,
        list: Seq[String]
      ) derives JsonRW
    
      val data = WriteData(true, 5, 3.14, "xyz", Seq("a", "b"))

      data.toJson
      // {"str":"xyz","bln":true,"list":["a","b"],"int":5,"dbl":3.14}