Never do this in your YouTube channel else your channel will...

 I have seen many YouTubers who are new put tags in their description box and for your information, this is against the YouTube community guidelines and your channel can even get Demonetized. This means that your channel can't display ads which will directly effect your revenue!

This is against the YouTube community guidelines as the YouTube algorithms gets tricked due to this and your video gets ranked in the search results.

Now let's talk about that how you can add tags in a legal way. You can describe things you are going to tell in your video. For example if you are telling in your video some ideas for evening snaks. So you can write that: "Hello everyone and today I will be telling you how to prepare evening snaks. These snaks are really easy and quick to make..." rather than tasty snaks, evening snaks quick recipies, etc.

So that's how you can make appropriate use of Tags in Description. Best of luck of your YouTube journey!