You can fetch all relevant Real User Monitoring metrics from the Dynatrace REST API. See here:
Hi, I need fetch the metrics of Dashboard ?
(I used this option in Appmon)
There is no combined dashboard fetch but you can get the individual metrics through the timeseries API.
Does that mean I can't get an Apdex rating?
My goal is to read "Apdex rating" through the API
Yes you can, fetch following apdex metric from the timeseries API
Can you write me an example of such a request?
I monitor page load time (with Key), Is it possible to retrieve through the API what page load time
Yes you can fetch all key performance metrics (including page load time) through the API.