diff --git a/src/ol/array.js b/src/ol/array.js
index 47dc5d0876..bb9796c096 100644
--- a/src/ol/array.js
+++ b/src/ol/array.js
@@ -194,8 +194,11 @@ export function equals(arr1, arr2) {
 
 
 /**
+ * Sort the passed array such that the relative order of equal elements is preverved.
+ * See https://en.wikipedia.org/wiki/Sorting_algorithm#Stability for details.
  * @param {Array<*>} arr The array to sort (modifies original).
- * @param {Function} compareFnc Comparison function.
+ * @param {!function(*, *): number} compareFnc Comparison function.
+ * @api
  */
 export function stableSort(arr, compareFnc) {
   const length = arr.length;
diff --git a/src/ol/util.js b/src/ol/util.js
index beecbdc9fa..2eee713b3d 100644
--- a/src/ol/util.js
+++ b/src/ol/util.js
@@ -44,6 +44,7 @@ let uidCounter_ = 0;
  *
  * @param {Object} obj The object to get the unique ID for.
  * @return {number} The unique ID for the object.
+ * @api
  */
 export function getUid(obj) {
   return obj.ol_uid || (obj.ol_uid = ++uidCounter_);