Integrating content design in a design system

Some good practices for documenting content design in your design system:

Document design and content guidelines together - don't isolate content design elsewhere. It's just another part of the puzzle so keep it on the same level.
Use realistic copy in examples. This is an easy win to provide better context and show how the component is used in product.
Create a clear list of do's and dont's. This provides easy clarification, especially for non-UX writers.
Consider inclusivity and accessibility.
Be specific and focused about your guidelines. If there's a must, clearly state that it's a must, and not a recommendation.