diff --git a/rejoiner/src/main/java/com/google/api/graphql/rejoiner/SchemaModule.java b/rejoiner/src/main/java/com/google/api/graphql/rejoiner/SchemaModule.java
index af61e49..ed797e5 100644
--- a/rejoiner/src/main/java/com/google/api/graphql/rejoiner/SchemaModule.java
+++ b/rejoiner/src/main/java/com/google/api/graphql/rejoiner/SchemaModule.java
@@ -38,6 +38,7 @@
 import graphql.schema.GraphQLList;
 import graphql.schema.GraphQLObjectType;
 import graphql.schema.GraphQLOutputType;
+import graphql.schema.GraphQLScalarType;
 
 import javax.annotation.Nullable;
 import javax.inject.Provider;
@@ -415,7 +416,7 @@ private GraphQLFieldDefinition methodToFieldDefinition(
     }
   }
 
-  ImmutableMap<java.lang.reflect.Type, GraphQLOutputType> javaTypeToScalarMap =
+  ImmutableMap<java.lang.reflect.Type, GraphQLScalarType> javaTypeToScalarMap =
       ImmutableMap.of(
           String.class, Scalars.GraphQLString,
           Integer.class, Scalars.GraphQLInt,
@@ -504,6 +505,7 @@ private ImmutableList<MethodMetadata> getMethodMetadata(
         } else {
           GqlInputConverter inputConverter =
               GqlInputConverter.newBuilder().add(requestDescriptor.getFile()).build();
+          addExtraType(requestDescriptor);
           Message message =
               ((Message.Builder) requestClass.getMethod("newBuilder").invoke(null)).build();
           String argName = getArgName(method.getParameterAnnotations()[i]);
@@ -517,6 +519,21 @@ private ImmutableList<MethodMetadata> getMethodMetadata(
           GraphQLArgument argument = GqlInputConverter.createArgument(requestDescriptor, argName);
           listBuilder.add(MethodMetadata.create(function, argument));
         }
+      } else if (isArg(method.getParameterAnnotations()[i])) {
+        if (javaTypeToScalarMap.containsKey(parameterType)) {
+          String argName = getArgName(method.getParameterAnnotations()[i]);
+          Function<DataFetchingEnvironment, ?> function =
+              environment -> environment.getArgument(argName);
+          GraphQLArgument argument =
+              GraphQLArgument.newArgument()
+                  .name(argName)
+                  .type(javaTypeToScalarMap.get(parameterType))
+                  .build();
+          listBuilder.add(MethodMetadata.create(function, argument));
+        } else {
+          throw new RuntimeException("Unknown arg type: " + parameterType.getName());
+        }
+
       } else if (DataFetchingEnvironment.class.isAssignableFrom(parameterType)) {
         listBuilder.add(MethodMetadata.create(Functions.identity()));
       } else {
@@ -539,6 +556,15 @@ private ImmutableList<MethodMetadata> getMethodMetadata(
     return listBuilder.build();
   }
 
+  private static boolean isArg(Annotation[] annotations) {
+    for (Annotation annotation : annotations) {
+      if (annotation.annotationType().isAssignableFrom(Arg.class)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   private static String getArgName(Annotation[] annotations) {
     for (Annotation annotation : annotations) {
       if (annotation.annotationType().isAssignableFrom(Arg.class)) {
diff --git a/schema/src/main/java/com/google/api/graphql/schema/protobuf/TimestampSchemaModule.java b/schema/src/main/java/com/google/api/graphql/schema/protobuf/TimestampSchemaModule.java
index 2b18a87..88f4cd4 100644
--- a/schema/src/main/java/com/google/api/graphql/schema/protobuf/TimestampSchemaModule.java
+++ b/schema/src/main/java/com/google/api/graphql/schema/protobuf/TimestampSchemaModule.java
@@ -34,8 +34,9 @@ Boolean isAfterNow(Timestamp timestamp) {
     return Instant.ofEpochSecond(timestamp.getSeconds()).isAfter(Instant.now());
   }
 
-  @SchemaModification(addField = "afterNow", onType = Timestamp.class)
+  @SchemaModification(addField = "localTime", onType = Timestamp.class)
   String localTime(Timestamp timestamp, @Arg("timezone") String timezone) {
+    // TODO: Arg should be required, optional should be optional
     return Instant.ofEpochSecond(timestamp.getSeconds()).atZone(ZoneId.of(timezone)).toString();
   }
 }