diff --git a/src/actions/GroupActions.js b/src/actions/GroupActions.js
index 8e5484bb8c..f3337eda25 100644
--- a/src/actions/GroupActions.js
+++ b/src/actions/GroupActions.js
@@ -18,6 +18,14 @@ import { asyncAction } from './actionCreators';
 
 const GroupActions = {};
 
+/**
+ * Create a GroupActions.fetchJoinedGroups action that represents an
+ * asyncronous request to fetch the groups to which a user is joined.
+ *
+ * @param {MatrixClient} matrixClient the matrix client to query.
+ * @returns {function} an asyncronous action of type
+ *                   GroupActions.fetchJoinedGroups.
+ */
 GroupActions.fetchJoinedGroups = function(matrixClient) {
     return asyncAction('GroupActions.fetchJoinedGroups', () => matrixClient.getJoinedGroups());
 };