diff --git a/lib/executor.js b/lib/executor.js
index 6f0cf34..61275be 100755
--- a/lib/executor.js
+++ b/lib/executor.js
@@ -1,15 +1,41 @@
 /**
  * Responsible for sequentially executing actions on the database
+ * @private
  */
 class Waterfall {
   constructor () {
+    /**
+     * This is the internal Promise object which resolves when all the tasks of the `Waterfall` are done.
+     *
+     * It will change any time `this.waterfall` is called, this is why there is a getter `this.guardian` which retrieves
+     * the latest version of the guardian.
+     * @type {Promise<void>}
+     * @private
+     */
     this._guardian = Promise.resolve()
   }
 
+  /**
+   * Returns a Promise which resolves when all tasks up to when this function is called are done.
+   *
+   * This Promise cannot reject.
+   * @return {Promise<void>}
+   */
   get guardian () {
     return this._guardian
   }
 
+  /**
+   * @callback Waterfall~function
+   * @param {...[*]} args
+   * @return {Promise<*>}
+   */
+
+  /**
+   *
+   * @param {Waterfall~function} func
+   * @return {Waterfall~function}
+   */
   waterfall (func) {
     return (...args) => {
       this._guardian = this.guardian.then(() => {