These are language independent general principles of Wikidata descriptions.
Avoid information that is likely to change edit
Words and phrases like "current", "incumbent", "expected", or "next year's" will eventually have to be changed. For example, if you were describing Tatsumi Kimishima, it would be better to use "fifth president of Nintendo" than to use "current president of Nintendo". While both are correct, the latter will change when Mr. Kimishima retires, while the former does not change. Just using "president of Nintendo" would also be appropriate, as it would provide enough information for successful disambiguation if, for example, there were numerous noteworthy individuals by the name of Tatsumi Kimishima.
For sportspeople, it is unwise to list the player's current team, as that also has the possibility to change. If you were describing Daniel Alves, it would be better to use "association football player from Brazil" than to use "association football player at FC Barcelona", because Daniel Alves' club may change.
Avoid opinionated, biased or promotional wording edit
Neutrality is a core value of Wikidata, Wikipedia and other Wikimedia projects. Try to keep descriptions neutral by avoiding opinionated or biased terms. In addition, avoid terminology that could be interpreted as promotional. "American novelist" is a neutral description while "the best novelist in America" is both opinionated and promotional.
Avoid controversial claims edit
Descriptions should try to reflect information both accurately and neutrally. If possible, you should avoid including controversial claims in descriptions. For example, it is better to describe the Pinnacle Islands as a "group of islands in East Asia" than a "group of Japanese islands" or a "group of Chinese islands". Remember, there will be a lot more information about an item on the page than just the description.
Follow Wikimedia namespace conventions edit
Wikidata contains items for several types of Wikimedia site pages that are found outside of a site's main namespace (for example, non-article pages in Wikipedia). These include templates, category pages, help pages, and Special pages. If an item is for Wikimedia site use only, it should mention the site in the description. This allows readers to know, at a glance, that they are not dealing with normal content.
Label: Top Gear
Description: Wikipedia disambiguation page
This item is the Wikipedia disambiguation page for things that are called Top Gear.
Description: Wikipedia portal showcasing content related to the field of history
Although the inclusion of "Portal:" in the title makes it clear to people that are familiar with Wikipedia that this is a Wikipedia portal, not everyone who uses Wikidata will know what that means, so specifying that it is a Wikipedia portal still is a good idea.
Descriptions are not definitions edit
The concept represented by the item is defined by the statements not the description. If you need to distinguish an item from another item, add the right statements with sources before you add a special description. Also when searching items don't rely on the description's correctness, check the statements to ensure you found the right item.