diff --git a/core/block.js b/core/block.js
index 625465bfb..684e6642e 100644
--- a/core/block.js
+++ b/core/block.js
@@ -72,6 +72,13 @@ Blockly.Block.obtain = function(workspace, prototypeName) {
   }
 };
 
+/**
+ * Optional text data that round-trips beween blocks and XML.
+ * Has no effect. May be used by 3rd parties for meta information.
+ * @type {?string}
+ */
+Blockly.Block.prototype.data = null;
+
 /**
  * Initialization for one block.
  * @param {!Blockly.Workspace} workspace The new block's workspace.
diff --git a/core/block_svg.js b/core/block_svg.js
index 9c0d42040..30d4fdfa8 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -315,7 +315,7 @@ Blockly.BlockSvg.prototype.snapToGrid = function() {
 /**
  * Returns a bounding box describing the dimensions of this block
  * and any blocks stacked below it.
- * @return {!Object} Object with height and width properties.
+ * @return {!{height: number, width: number}} Object with height and width properties.
  */
 Blockly.BlockSvg.prototype.getHeightWidth = function() {
   var height = this.height;
diff --git a/core/connection.js b/core/connection.js
index 96799bfe2..a459d2514 100644
--- a/core/connection.js
+++ b/core/connection.js
@@ -493,7 +493,7 @@ Blockly.Connection.prototype.tighten_ = function() {
  *     in the database and the current location (as a result of dragging).
  * @param {number} dy Vertical offset between this connection's location
  *     in the database and the current location (as a result of dragging).
- * @return {!Object} Contains two properties: 'connection' which is either
+ * @return {!{connection: ?Blockly.Connection, radius: number}} Contains two properties: 'connection' which is either
  *     another connection or null, and 'radius' which is the distance.
  */
 Blockly.Connection.prototype.closest = function(maxLimit, dx, dy) {
diff --git a/core/xml.js b/core/xml.js
index 070c1610f..2fda8caa0 100644
--- a/core/xml.js
+++ b/core/xml.js
@@ -99,8 +99,6 @@ Blockly.Xml.blockToDom_ = function(block) {
   }
 
   if (block.data) {
-    // Optional text data that round-trips beween blocks and XML.
-    // Has no effect.  May be used by 3rd parties for meta information.
     var dataElement = goog.dom.createDom('data', null, block.data);
     element.appendChild(dataElement);
   }
@@ -428,8 +426,6 @@ Blockly.Xml.domToBlockHeadless_ =
         }
         break;
       case 'data':
-        // Optional text data that round-trips beween blocks and XML.
-        // Has no effect.  May be used by 3rd parties for meta information.
         block.data = xmlChild.textContent;
         break;
       case 'title':