This is an excellent content design primer on the Digital Access Solutions
And Assistive Technology (DASAT) blog by Nikki Fiedler, Co-Founder of Content Design Hub.

Content design is about function: does this help the person complete their task? If someone can’t find, understand or use the information, the content hasn’t done its job, no matter how polished it reads.

Don't assume everyone you work with knows what content design is, even if they probably should. Send them to this or similar articles if you need to explain how it works and why it's different to good, old-fashioned copywriting.