It seems the Asana API does not respond ETag or Last-Modified HTTP headers. Those headers help client-side caching by letting clients ask for any request “is the version I have in my cache up-to-date?”.
It is standard HTTP and it is implemented by many API services (for example, Github’s API) and API clients, avoiding to have to implement specific behavior for Asana.
This would be a great counterpart to the events API.
Thanks for the request! I’ll pass this on to our Platform team.