How can I add custom metadata to calender objects via MS Graph API?

Question

I'm trying to write a calendar sync using the MS Graph API, i.e. I'm trying to sync events in a local DB to one or several newly created M365 calendars via Graph. In order to keep track of the created calendars, I need to store custom metadata with each calendar. It appears that single-value extended property is the way to add my local ID to the created calendar.

Unfortunately I fail to grasp how to do that: the documentation describes a simple enough request to write the data:

{
  "singleValueExtendedProperties": [
      {
         "id":"String {66f5a359-4659-4830-9070-00047ec6ac6e} Name Color",
         "value":"Green"
      }
    ]
}

But the json references a GUID which, in its documentation, references the Exchange Server Protocols Master Property List but I don't understand how they're all connected with each other: do I need to select an ID from the Exchange Server Protocols Master Property List? Is it possible to create a custom GUID? Do I need to create a schema extension (which doesn't seem to be possible for calendar resource types)?

So, how do I add custom metadata to my calendars?

Answer 1

When you create a custom named property, it must be identified by the extended property type, property set identifier, and a string name.

Extended property identifier (id):

<property_type> <property_set_guid> Name <name_of_custom_property>

Property type specifies the data type of a property value. Common values are String, Integer, StringArray and IntegerArray.

Property set is a set of attributes, identified by a GUID. Several of the more common property sets are described here. You can use GUID for PS_PUBLIC_STRINGS ({00020329-0000-0000-C000-000000000046}) property set name.

String name is a name of your custom property.

Example to create an extended property for a calendar.

PATCH https://graph.microsoft.com/v1.0/me/calendars/{calendar-id}

Content-Type: application/json

{
    "singleValueExtendedProperties": [
        {
            "id": "String {00020329-0000-0000-C000-000000000046} Name YourPropertyName",
            "value": "PropertyValue" // local ID you want to store
        }
    ]
}

Get property value by using $expand query with $filter inside the expand.

GET https://graph.microsoft.com/v1.0/me/calendars/{calendar-id}?$expand=singleValueExtendedProperties($filter=id eq 'String {00020329-0000-0000-C000-000000000046} Name YourPropertyName')

Resources:

Commonly Used Property Sets