The coverage.json endpoint is used to find what surveys (dates and survey resource IDs) have had AI data processed. The response not only provides the surveys that have AI data, but the precise version of the data (systemVersion), and which feature and attribute class IDs are available on it.
https://api.nearmap.com/ai/features/v4/coverage.json?point={lon},{lat}apikey={your_nearmap_api_key}