diff --git a/app/controllers/SlideController.js b/app/controllers/SlideController.js
index 3795faf..f503b7e 100644
--- a/app/controllers/SlideController.js
+++ b/app/controllers/SlideController.js
@@ -9,16 +9,22 @@ const robots = {
 const controller = {};
 
 controller.post = async (req, res) => {
-    let content = { lang, author, searchTerm, font, prefix, numberOfSlides } = req.body;
+    let content = { lang = 'en', author = '', searchTerm, font = 'Roboto', prefix, numberOfSlides = 7 } = req.body;
     content.id = generateRandomId();
 
+    if(!searchTerm)
+      return res.status(400).json({ error: 'search term missing' });
+
+    if(numberOfSlides > 20)
+      return res.status(400).json({ error: 'number of slides exceeded the limit' });
+
     try {
       content = await robots.text.start(content);
       content = await robots.image.start(content);
       await robots.powerPoint.start(content);
       res.json({ slideId: content.id });
     } catch(error) {
-      res.status(400).json({ error });
+      res.status(500).json({ error });
     }
 }