diff --git a/lib/defaults/index.js b/lib/defaults/index.js
index d7ed025..da3db72 100644
--- a/lib/defaults/index.js
+++ b/lib/defaults/index.js
@@ -13,12 +13,28 @@ var DEFAULT_CONTENT_TYPE = {
   'Content-Type': 'application/x-www-form-urlencoded'
 };
 
+/**
+ * If the headers object is not undefined and the Content-Type property of the headers object
+ * is undefined, then set the Content-Type property of the headers object to the value passed
+ * in
+ *
+ * @param {Object<string, string>} headers - The headers object that will be sent to the server.
+ * @param {any} value - The value of the Content-Type header.
+ *
+ * @returns {void}
+ */
 function setContentTypeIfUnset(headers, value) {
   if (!utils.isUndefined(headers) && utils.isUndefined(headers['Content-Type'])) {
     headers['Content-Type'] = value;
   }
 }
 
+/**
+ * If the browser has an XMLHttpRequest object, use the XHR adapter, otherwise use the HTTP
+ * adapter
+ *
+ * @returns {Function}
+ */
 function getDefaultAdapter() {
   var adapter;
   if (typeof XMLHttpRequest !== 'undefined') {
@@ -31,6 +47,16 @@ function getDefaultAdapter() {
   return adapter;
 }
 
+/**
+ * It takes a string, tries to parse it, and if it fails, it returns the stringified version
+ * of the input
+ *
+ * @param {any} rawValue - The value to be stringified.
+ * @param {Function} parser - A function that parses a string into a JavaScript object.
+ * @param {Function} encoder - A function that takes a value and returns a string.
+ *
+ * @returns {string} A stringified version of the rawValue.
+ */
 function stringifySafely(rawValue, parser, encoder) {
   if (utils.isString(rawValue)) {
     try {