diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
index cd660cb..09402e6 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
@@ -256,7 +256,8 @@ public static function baseFieldDefinitions($entity_type) {
       ->setDescription(t('The ID of the aggregator feed.'))
       ->setReadOnly(TRUE);
 
-    // @todo Why does this entity type not have an UUID field?
+    // @todo Add a UUID field for this entity type in
+    // https://drupal.org/node/2149841.
 
     $fields['title'] = FieldDefinition::create('string')
       ->setLabel(t('Title'))
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Item.php b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Item.php
index 818f463..62dfdd9 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Item.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Item.php
@@ -107,7 +107,7 @@ public static function baseFieldDefinitions($entity_type) {
       ->setLabel(t('Author'))
       ->setDescription(t('The author of the feed item.'));
 
-    // @todo Convert to a text field?
+    // @todo Convert to a text field in https://drupal.org/node/2149845.
     $fields['description'] = FieldDefinition::create('string')
       ->setLabel(t('Description'))
       ->setDescription(t('The body of the feed item.'));
@@ -117,7 +117,7 @@ public static function baseFieldDefinitions($entity_type) {
       ->setLabel(t('Posted timestamp'))
       ->setDescription(t('Posted date of the feed item, as a Unix timestamp.'));
 
-    // @todo Why not a UUID field?
+    // @todo Convert to a real UUID field in https://drupal.org/node/2149851.
     $fields['guid'] = FieldDefinition::create('string')
       ->setLabel(t('GUID'))
       ->setDescription(t('Unique identifier for the feed item.'));
diff --git a/core/modules/comment/lib/Drupal/comment/Entity/Comment.php b/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
index 6c411ba..e6402aa 100644
--- a/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
+++ b/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
@@ -430,7 +430,8 @@ public static function baseFieldDefinitions($entity_type) {
       ->setLabel(t('Entity type'))
       ->setDescription(t('The entity type to which this comment is attached.'));
 
-    // @todo Change to an entity_reference field?
+    // @todo Convert to aa entity_reference field in
+    // https://drupal.org/node/2149859.
     $fields['field_id'] = FieldDefinition::create('string')
       ->setLabel(t('Field ID'))
       ->setDescription(t('The comment field id.'));
diff --git a/core/modules/file/lib/Drupal/file/Entity/File.php b/core/modules/file/lib/Drupal/file/Entity/File.php
index 0638cae..5da26d2 100644
--- a/core/modules/file/lib/Drupal/file/Entity/File.php
+++ b/core/modules/file/lib/Drupal/file/Entity/File.php
@@ -247,7 +247,7 @@ public static function baseFieldDefinitions($entity_type) {
       ->setLabel(t('File MIME type'))
       ->setDescription(t("The file's MIME type."));
 
-    // @todo In what world does it make sense for a 'filesize' property to be a boolean field?
+    // @todo Convert to an integer field in https://drupal.org/node/2149877.
     $fields['filesize'] = FieldDefinition::create('boolean')
       ->setLabel(t('File size'))
       ->setDescription(t('The size of the file in bytes.'));
diff --git a/core/modules/user/lib/Drupal/user/Entity/User.php b/core/modules/user/lib/Drupal/user/Entity/User.php
index 1b1128a..660f596 100644
--- a/core/modules/user/lib/Drupal/user/Entity/User.php
+++ b/core/modules/user/lib/Drupal/user/Entity/User.php
@@ -519,6 +519,8 @@ public static function baseFieldDefinitions($entity_type) {
       ->setDescription(t('The email address used for initial account creation.'))
       ->setFieldSetting('default_value', '');
 
+    // @todo Convert this to entity_reference_field, see
+    // https://drupal.org/node/2044859.
     $fields['roles'] = FieldDefinition::create('string')
       ->setLabel(t('Roles'))
       ->setDescription(t('The roles the user has.'));