diff --git a/chart/main.js b/chart/main.js
index ad8057c..9a76407 100644
--- a/chart/main.js
+++ b/chart/main.js
@@ -5,10 +5,10 @@ const request = require('request');
 
 /**
  * Graph generation
- * @param from_currency {String} - The currency that is being converted
- * @param conv_currency {String} - The currency to be converted into
- * @param start_date {String} - Start date of the period
- * @param end_date {String} - End date of the period
+ * @param {String} from_currency - The currency that is being converted
+ * @param {String} conv_currency - The currency to be converted into
+ * @param {String} start_date - Start date of the period
+ * @param {String} end_date - End date of the period
  * @returns {Promise<Error|string>}
  */
 async function gen_chart(from_currency, conv_currency, start_date, end_date) {
@@ -77,8 +77,8 @@ async function gen_chart(from_currency, conv_currency, start_date, end_date) {
 
 /**
  * Saving a graph to a file
- * @param url {String} - URL (or Buffer) to the chart
- * @param filename {String} - filename
+ * @param {String} url  - URL (or Buffer) to the chart
+ * @param {String} filename - filename
  */
 function save_chart(url, filename) {
     if (!fs.existsSync('../charts')) fs.mkdirSync('../charts');
diff --git a/collect-currency/save_crypto.js b/collect-currency/save_crypto.js
index 3d78fbe..d2d6988 100644
--- a/collect-currency/save_crypto.js
+++ b/collect-currency/save_crypto.js
@@ -2,6 +2,11 @@ const config = require('../config/main.js')();
 const axios = require('axios');
 const pool = require('../database/postgresql.js');
 
+
+/**
+ * Saves exchange rate of the cryptocurrency
+ * @return {Object}
+ */
 function save_fiat() {
     if (!config['currency']['collecting']['crypto']) return;
     const depth = config['currency']['coinapiKeys']
@@ -47,6 +52,13 @@ function save_fiat() {
     );
 }
 
+/**
+ * Changing API keys
+ * @param {Array} list - List of all keys
+ * @param active - Active API key
+ * @returns {number} - Outputs the number of the key that should work
+ */
+
 function rotate_key(list, active) {
     return active[0] = (active + 1) % list.length;
 }
diff --git a/collect-currency/save_fiat.js b/collect-currency/save_fiat.js
index bf27595..112edc8 100644
--- a/collect-currency/save_fiat.js
+++ b/collect-currency/save_fiat.js
@@ -2,6 +2,10 @@ const pool = require('../database/postgresql.js');
 const axios = require('axios');
 const config = require('../config/main.js')();
 
+/**
+ * Saves exchange rate of the fiat currency
+ * @returns {Object} -
+ */
 async function save_fiat() {
     if (!config['currency']['collecting']['fiat']) return;
 
diff --git a/database/main.js b/database/main.js
index 089ec87..fe59025 100644
--- a/database/main.js
+++ b/database/main.js
@@ -1,5 +1,14 @@
 const pool = require('./postgresql.js');
 
+
+/**
+ * Getting the currency exchange rate for a specific day
+ * @param from_currency {String}
+ * @param conv_currency {String}
+ * @param date
+ * @returns {Promise<*|Error>}
+ */
+
 async function getDay(from_currency, conv_currency, date) {
     if (!from_currency || !conv_currency) return new Error('fromCurrency and convCurrency are required');
     else if (!date) return new Error('date is required')
@@ -16,6 +25,15 @@ async function getDay(from_currency, conv_currency, date) {
     return data['rows'][0];
 }
 
+/**
+ * Getting the exchange rate for a certain period
+ * @param {String} from_currency - The currency that is being converted
+ * @param {String} conv_currency - The currency to be converted into
+ * @param {String} start_date - Start date of the period
+ * @param {String} end_date - End date of the period
+ * @returns {Promise<*|Error>}
+ */
+
 async function getPeriod(from_currency, conv_currency, start_date, end_date) {
     if (!from_currency || !conv_currency) return new Error('from_currency and conv_currency are required');
     else if(!start_date || !end_date) return new Error('start_date and end_date are required')