It's best to follow the advice from Apple or Google Play.
We did a little research for you and also found some advice in this article by the Application Developers Alliance. They recommend the following:
- Use targeted keywords in your app description.
- Search the app store to identify marketable keywords, and then incorporate those words into app titles and descriptions.
- Draft titles and descriptions that sound natural and differentiate the app from others. Avoid highly competitive and generic keywords.
- Keywords are like hashtags on Twitter. Do not use any more than necessary, and do not force them.
- If you have more than one related publication, consider including the name of the second app in the title field of the other one.