Document API call throttling limits

[AndrewRudin1]

Please provide documentation on the limits on the number of REST API calls that can be made for ArcGIS Online or ArcGIS Enterprise.

When I try to iterate over the thousands of items in my AGOL org and obtain data about them using the REST API, I will often get errors like the following:

{"error":{"code":400,"messageCode":"GWM_0026","message":"Too many requests. Please try again later.","details":[]}}

These messages don't appear at first, but after a few minutes of a tools like FME or Python iterating and calling REST endpoints, this message will appear.  If I knew what the limits were I could tell my FME or Python script to slow down to stay within the limits.  The only documentation i've seen on API limits talks about how many responses you can get for something like a call against a feature service.  They don't talk about how many times you can call that endpoint per second or per minute.