schema: {
       model: {
               id: "ProductID",
               fields: {
               ProductID: { editable: false, nullable: true },
               ProductName: {
                   validation: {
                  required: true,
                  productnamevalidation: function (input) {
                       if (input.is("[name='ProductName']") && input.val() != "") {
                        input.attr("data-productnamevalidation-msg", "Product Name should start with capital letter");
                    return /^[A-Z]/.test(input.val());
                 }

                  return true;
              }
           }
         },
         UnitPrice: { type: "number", validation: { required: true, 
         min: 1} },
         Discontinued: { type: "boolean" },
         UnitsInStock: { type: "number", validation: { min: 0, 
         required: true} }
         }
     }

• Custom validator editing From Kendo Demo