Q:

Is there an API resource for the Reminders object existing in Google Calendars' GUI?

in google calendar you can create 3 different objects:

Event
Reminder
Task

I try to figure out which fields are provided by the google calendar for reminders.
I found the documentation for calendar events: https://developers.google.com/calendar/v3/reference/events
And I also found the documentation for calendar tasks (and task lists): https://developers.google.com/tasks/v1/reference/tasks
So I know which fields are provided and what there meaning is.
But unfortunately I am unable to find the documentation for the reminders and which fields they offer.
Does anyone know where/how to find the documentation for the reminders? Or which fields they provide in total? Or are they just events from a special kind?

A:

IMPORTANT:
Unfortunately, at the moment there is no API resource for the new GUI reminder object. So ATM it can only be used through the GUI.
There is an issue created in the Public Issue Tracker for creating an API for reminders. Please use this link and add your two cents. Thank you !

You are on the correct documentation site for the reminders. You see, reminders are a property of the Event resource.
If you take a deeper look at the Event resource structure (scrolling down) you will find the property "reminders":
 "reminders": {
    "useDefault": boolean,
    "overrides": [
      {
        "method": string,
        "minutes": integer
      }
    ]
  },

Further down you have the Value, Description and Notes for each property ordered by Property Name.
Here is a screenshot of the reminders property details:

Here you have a bit more explanation about the concept of reminders in Google Calendar.
And this help page also has some useful.
But I believe the most important concept is that of the Default reminder which is reminder setting that applies to all events created in that Calendar.
Note:
The Calendar Event's reminder property is set to use the Default Reminder settings of the calendar to which it belongs by default. And can be overridden by specific settings for the event in question.

