diff --git a/angel_graphql/example/main.dart b/angel_graphql/example/main.dart
index d9ed9dec..06310af2 100644
--- a/angel_graphql/example/main.dart
+++ b/angel_graphql/example/main.dart
@@ -24,11 +24,16 @@ main() async {
     description: 'A simple API that manages your to-do list.',
     fields: [
       field(
-        'todo',
+        'todos',
         type: listType(convertDartType(Todo).nonNullable()),
-        resolve: resolveFromService(todoService),
+        resolve: resolveViaServiceIndex(todoService),
+      ),
+      field(
+        'todo',
+        type: convertDartType(Todo),
+        resolve: resolveViaServiceRead(todoService),
         arguments: [
-          new GraphQLFieldArgument('id', graphQLId),
+          new GraphQLFieldArgument('id', graphQLId.nonNullable()),
         ],
       ),
     ],
@@ -39,10 +44,14 @@ main() async {
   app.all('/graphql', graphQLHttp(new GraphQL(schema)));
   app.get('/graphiql', graphiql());
 
-  await todoService.create({'text': 'Clean your room!', 'completed': true});
-  await todoService.create({'text': 'Take out the trash', 'completed': false});
+  await todoService
+      .create({'text': 'Clean your room!', 'completion_status': 'COMPLETE'});
   await todoService.create(
-      {'text': 'Become a billionaire at the age of 5', 'completed': false});
+      {'text': 'Take out the trash', 'completion_status': 'INCOMPLETE'});
+  await todoService.create({
+    'text': 'Become a billionaire at the age of 5',
+    'completion_status': 'INCOMPLETE'
+  });
 
   var server = await http.startServer('127.0.0.1', 3000);
   var uri =
@@ -67,5 +76,4 @@ class Todo extends Model {
 }
 
 @GraphQLDocumentation(description: 'The completion status of a to-do item.')
-enum CompletionStatus {
-  COMPLETE, INCOMPLETE }
+enum CompletionStatus { COMPLETE, INCOMPLETE }
diff --git a/angel_graphql/lib/src/graphql_http.dart b/angel_graphql/lib/src/graphql_http.dart
index 2da0c944..c936be75 100644
--- a/angel_graphql/lib/src/graphql_http.dart
+++ b/angel_graphql/lib/src/graphql_http.dart
@@ -55,7 +55,7 @@ RequestHandler graphQLHttp(GraphQL graphQl) {
 
       errors
           .addAll(e.errors.map((ee) => new GraphQLExceptionError(ee)).toList());
-      throw new GraphQLException(errors);
+      return new GraphQLException(errors).toJson();
     } on SyntaxError catch (e) {
       return new GraphQLException.fromSourceSpan(e.message, e.span);
     } on GraphQLException catch (e) {
diff --git a/angel_graphql/lib/src/resolvers.dart b/angel_graphql/lib/src/resolvers.dart
index 94f55c4a..df19a948 100644
--- a/angel_graphql/lib/src/resolvers.dart
+++ b/angel_graphql/lib/src/resolvers.dart
@@ -1,25 +1,30 @@
 import 'package:angel_framework/angel_framework.dart';
 import 'package:graphql_schema/graphql_schema.dart';
 
-/// A GraphQL resolver that indexes an Angel service.
-///
-/// If [enableRead] is `true`, and the [idField] is present in the input,
-/// a `read` will be performed, rather than an `index`.
+/// A GraphQL resolver that `index`es an Angel service.
 ///
 /// The arguments passed to the resolver will be forwarded to service, and the
 /// service will receive [Providers.graphql].
-GraphQLFieldResolver<Value, Serialized> resolveFromService<Value, Serialized>(
-    Service service,
-    {String idField: 'id',
-    bool enableRead: true}) {
+GraphQLFieldResolver<Value, Serialized>
+    resolveViaServiceIndex<Value, Serialized>(Service service,
+        {String idField: 'id'}) {
   return (_, arguments) async {
     var params = {'query': arguments, 'provider': Providers.graphql};
 
-    if (enableRead && arguments.containsKey(idField)) {
-      var id = arguments.remove(idField);
-      return await service.read(id, params) as Value;
-    }
-
     return await service.index(params) as Value;
   };
 }
+
+/// A GraphQL resolver that `read`s a single value from an Angel service.
+///
+/// The arguments passed to the resolver will be forwarded to service, and the
+/// service will receive [Providers.graphql].
+GraphQLFieldResolver<Value, Serialized>
+    resolveViaServiceRead<Value, Serialized>(Service service,
+        {String idField: 'id'}) {
+  return (_, arguments) async {
+    var params = {'query': arguments, 'provider': Providers.graphql};
+    var id = arguments.remove(idField);
+    return await service.read(id, params) as Value;
+  };
+}
diff --git a/graphql_server/lib/graphql_server.dart b/graphql_server/lib/graphql_server.dart
index 820c532a..01cab90a 100644
--- a/graphql_server/lib/graphql_server.dart
+++ b/graphql_server/lib/graphql_server.dart
@@ -238,9 +238,8 @@ class GraphQL {
         if (defaultValue != null || argumentDefinition.defaultsToNull) {
           coercedValues[argumentName] = defaultValue;
         } else if (argumentType is GraphQLNonNullableType) {
-          throw new GraphQLException.fromSourceSpan(
-              'Missing value for argument "$argumentName".',
-              value.valueOrVariable.span);
+          throw new GraphQLException.fromMessage(
+              'Missing value for argument "$argumentName".');
         } else {
           continue;
         }
diff --git a/graphql_server/lib/introspection.dart b/graphql_server/lib/introspection.dart
index 1fe80751..a4a6ede3 100644
--- a/graphql_server/lib/introspection.dart
+++ b/graphql_server/lib/introspection.dart
@@ -418,6 +418,10 @@ List<GraphQLType> _fetchAllTypesFromObject(GraphQLObjectType objectType) {
     } else {
       types.addAll(_fetchAllTypesFromType(field.type));
     }
+
+    for (var argument in field.arguments ?? <GraphQLFieldArgument>[]) {
+      types.addAll(_fetchAllTypesFromType(argument.type));
+    }
   }
 
   return types;