diff --git a/tools/exp/props/funcprop.go b/tools/exp/props/funcprop.go
index 7dd70fa..31eb664 100644
--- a/tools/exp/props/funcprop.go
+++ b/tools/exp/props/funcprop.go
@@ -135,7 +135,7 @@ func (p *FunctionalPropertyGenerator) funcs() []*codegen.Method {
 				join(kindIndexFns),
 				jen.Return(jen.Lit(-1)),
 			},
-			jen.Commentf("%s computes an arbitrary value for indexing this kind of value.", kindIndexMethod),
+			jen.Commentf("%s computes an arbitrary value for indexing this kind of value. This is a leaky API detail only for folks looking to replace the go-fed implementation. Applications should not use this method.", kindIndexMethod),
 		),
 	}
 	if p.HasNaturalLanguageMap {
@@ -320,19 +320,18 @@ func (p *FunctionalPropertyGenerator) serializationFuncs() (*codegen.Method, *co
 		deserializeFns = deserializeFns.If(
 			jen.List(
 				jen.Id("v"),
-				jen.Id("handled"),
 				jen.Err(),
 			).Op(":=").Add(kind.DeserializeFn.Clone().Call(
 				jen.Id("i"),
 			)),
-			jen.Id("handled"),
+			jen.Err().Op("!=").Nil(),
 		).Block(
 			jen.Id(codegen.This()).Op(":=").Op("&").Id(p.StructName()).Values(
 				values,
 			),
 			jen.Return(
 				jen.Id(codegen.This()),
-				jen.Err(),
+				jen.Nil(),
 			),
 		)
 	}
@@ -344,7 +343,15 @@ func (p *FunctionalPropertyGenerator) serializationFuncs() (*codegen.Method, *co
 			[]jen.Code{jen.Id("i").Interface()},
 			[]jen.Code{jen.Op("*").Id(p.StructName()), jen.Error()},
 			[]jen.Code{
-				p.addUnknownDeserializeCode(deserializeFns),
+				p.addUnknownDeserializeCode(deserializeFns).Else().Block(
+					jen.Return(
+						jen.Nil(),
+						jen.Qual("fmt", "Errorf").Call(
+							jen.Lit("could not deserialize %q property"),
+							jen.Lit(p.PropertyName()),
+						),
+					),
+				),
 				jen.Return(
 					jen.Nil(),
 					jen.Nil(),
@@ -653,7 +660,7 @@ func (p *FunctionalPropertyGenerator) multiTypeFuncs() []*codegen.Method {
 			isLanguageMapMethod,
 		)
 	}
-	methods = append(methods, codegen.NewCommentedPointerMethod(
+	methods = append(methods, codegen.NewCommentedValueMethod(
 		p.GetPrivatePackage().Path(),
 		hasAnyMethodName,
 		p.StructName(),
@@ -816,7 +823,7 @@ func (p *FunctionalPropertyGenerator) unknownMemberDef() jen.Code {
 
 // addUnknownDeserializeCode generates the "else if it's a []byte" code used for
 // deserializing unknown values.
-func (p *FunctionalPropertyGenerator) addUnknownDeserializeCode(existing jen.Code) jen.Code {
+func (p *FunctionalPropertyGenerator) addUnknownDeserializeCode(existing jen.Code) *jen.Statement {
 	if len(p.Kinds) > 0 {
 		existing = jen.Add(existing, jen.Else())
 	}
diff --git a/tools/exp/props/nonfuncprop.go b/tools/exp/props/nonfuncprop.go
index 9087952..ec2a8b5 100644
--- a/tools/exp/props/nonfuncprop.go
+++ b/tools/exp/props/nonfuncprop.go
@@ -7,6 +7,10 @@ import (
 	"sync"
 )
 
+const (
+	atMethodName = "At"
+)
+
 // NonFunctionalPropertyGenerator produces Go code for properties that can have
 // more than one value. The resulting property is a type that is a list of
 // iterators; each iterator is a concrete struct type. The property can be
@@ -63,7 +67,7 @@ func (p *NonFunctionalPropertyGenerator) Definitions() (*codegen.Struct, *codege
 		property := codegen.NewTypedef(
 			jen.Commentf("%s is the non-functional property %q. It is permitted to have one or more values, and of different value types.", p.StructName(), p.PropertyName()),
 			p.StructName(),
-			jen.Index().Id(p.iteratorTypeName().CamelName),
+			jen.Index().Op("*").Id(p.iteratorTypeName().CamelName),
 			methods,
 			funcs)
 		iterator := p.elementTypeGenerator().Definition()
@@ -80,6 +84,15 @@ func (p *NonFunctionalPropertyGenerator) iteratorTypeName() Identifier {
 	}
 }
 
+// iteratorInterfaceName gets the interface name for the iterator.
+//
+// TODO: Fix this kluge, which must be kept in sync with
+// PropertyGenerator.InterfaceName().
+func (p *NonFunctionalPropertyGenerator) iteratorInterfaceName() string {
+	id := p.iteratorTypeName()
+	return fmt.Sprintf("%sInterface", id.CamelName)
+}
+
 // elementTypeGenerator produces a FunctionalPropertyGenerator for the iterator
 // type.
 func (p *NonFunctionalPropertyGenerator) elementTypeGenerator() *FunctionalPropertyGenerator {
@@ -116,7 +129,7 @@ func (p *NonFunctionalPropertyGenerator) funcs() []*codegen.Method {
 				/*ret=*/ nil,
 				[]jen.Code{
 					jen.Op("*").Id(codegen.This()).Op("=").Append(
-						jen.Index().Id(p.iteratorTypeName().CamelName).Values(
+						jen.Index().Op("*").Id(p.iteratorTypeName().CamelName).Values(
 							jen.Values(dict),
 						),
 						jen.Op("*").Id(codegen.This()).Op("..."),
@@ -135,7 +148,7 @@ func (p *NonFunctionalPropertyGenerator) funcs() []*codegen.Method {
 				[]jen.Code{
 					jen.Op("*").Id(codegen.This()).Op("=").Append(
 						jen.Op("*").Id(codegen.This()),
-						jen.Id(p.iteratorTypeName().CamelName).Values(
+						jen.Op("&").Id(p.iteratorTypeName().CamelName).Values(
 							dict,
 						),
 					),
@@ -181,7 +194,7 @@ func (p *NonFunctionalPropertyGenerator) funcs() []*codegen.Method {
 					jen.Op("*").Id(codegen.This()),
 				).Index(
 					jen.Len(jen.Op("*").Id(codegen.This())).Op("-").Lit(1),
-				).Op("=").Id(p.iteratorTypeName().CamelName).Values(),
+				).Op("=").Op("&").Id(p.iteratorTypeName().CamelName).Values(),
 				jen.Op("*").Id(codegen.This()).Op("=").Parens(
 					jen.Op("*").Id(codegen.This()),
 				).Index(
@@ -249,7 +262,7 @@ func (p *NonFunctionalPropertyGenerator) funcs() []*codegen.Method {
 				jen.Return(jen.False()),
 			},
 			jen.Commentf("%s computes whether another property is less than this one. Mixing types results in a consistent but arbitrary ordering", lessMethod)))
-	// Kind Method
+	// KindIndex Method
 	methods = append(methods,
 		codegen.NewCommentedValueMethod(
 			p.GetPrivatePackage().Path(),
@@ -300,6 +313,19 @@ func (p *NonFunctionalPropertyGenerator) funcs() []*codegen.Method {
 		},
 		jen.Commentf("%s compares two instances of this property with an arbitrary but stable comparison.", compareLessMethod),
 	))
+	// At Method
+	methods = append(methods, codegen.NewCommentedValueMethod(
+		p.GetPrivatePackage().Path(),
+		atMethodName,
+		p.StructName(),
+		[]jen.Code{jen.Id("index").Int()},
+		[]jen.Code{jen.Qual(p.GetPublicPackage().Path(), p.iteratorInterfaceName())},
+		[]jen.Code{
+			jen.Return(
+				jen.Id(codegen.This()).Index(jen.Id("index")),
+			),
+		},
+		jen.Commentf("%s returns the property value for the specified index.", atMethodName)))
 	methods = append(methods, p.commonMethods()...)
 	return methods
 }
@@ -369,7 +395,7 @@ func (p *NonFunctionalPropertyGenerator) serializationFuncs() (*codegen.Method,
 		).Block(
 			jen.Id(codegen.This()).Op("=").Append(
 				jen.Id(codegen.This()),
-				jen.Op("*").Id("p"),
+				jen.Id("p"),
 			),
 		)
 	}
@@ -379,7 +405,7 @@ func (p *NonFunctionalPropertyGenerator) serializationFuncs() (*codegen.Method,
 		[]jen.Code{jen.Id("m").Map(jen.String()).Interface()},
 		[]jen.Code{jen.Id(p.StructName()), jen.Error()},
 		[]jen.Code{
-			jen.Var().Id(codegen.This()).Index().Id(p.iteratorTypeName().CamelName),
+			jen.Var().Id(codegen.This()).Index().Op("*").Id(p.iteratorTypeName().CamelName),
 			jen.If(
 				jen.List(
 					jen.Id("i"),
diff --git a/tools/exp/props/property.go b/tools/exp/props/property.go
index 0310b8c..249a2de 100644
--- a/tools/exp/props/property.go
+++ b/tools/exp/props/property.go
@@ -20,7 +20,7 @@ const (
 	lenMethod                 = "Len"
 	swapMethod                = "Swap"
 	lessMethod                = "Less"
-	kindIndexMethod           = "kindIndex"
+	kindIndexMethod           = "KindIndex"
 	serializeMethod           = "Serialize"
 	deserializeMethod         = "Deserialize"
 	nameMethod                = "Name"