Currently the chart.description property accepts a string.

If there was a chart.descriptionFormatter or similar property that expected a function. If this function was passed the chart data then it would be fairly trivial to make dynamic descriptions.

This would be fantastic for accessibility too in dynamic cases such as stock charts. Knowing that it is a line chart the developer could easily write a function that could return something along the lines of:

"This is a line chart showing Acme Co's stock price between {startDate} and {endDate}. In that period the price has [risen to|fallen to|remained stable at] ${price}. Volatility in the same period has been measured at {v}"

By making it generic it can support all chart types and it puts the onus on the developer but allowing for flexibility.