The description is the space most channels neglect. The D Score evaluates five variables and combines them into a number that tells you what to change first, read on a scale from ineffective to strong description.
How well the first lines explain the video and connect with the thumbnail and the title.
Coherent presence of the title's keywords, without stuffing the text.
Visual order: paragraphs, timestamps, separators and well-organized links.
Calls to action: subscribing, your own links and an invitation to join the conversation.
Credits, resources and extra information that add value for people already watching.
The D Score is calculated when you share the video's description. It doesn't change the ELM Score or the Clickability Index: it is an independent reading of a part of the video that almost always gets left for last.