400 Bad Request with MS Graph when adding list items - powershell

Question

For the life of me I can't successfully add SharePoint list items. I have in the past, now I'm stumped, using either Invoke-WebRequest or Invoke-RestMethod. I am able to update (PATCH) without issue, and can do all sorts of GET operations against the same sites, lists, items, etc.
Here's a fiddler capture of my actual HTTP POST request (Guid's fudged):
POST https://graph.microsoft.com/v1.0/sites/2df3a5af-979d-46d6-b24d-14e4e4b58aa9/lists/2252b849-53f9-4816-bc0b-d9183357c702/items HTTP/1.1
Content-Type: application/json
Authorization: Bearer eyJ0f...
User-Agent: MSGraphPSEssentials/0.4.0
Host: graph.microsoft.com
Content-Length: 537
{
"Fields": {
"AccountStatus": "Enabled",
"DisplayName": "Fictional User 1",
"UserId": "67853e89-65a9-431d-a3b1-1d60ab74dc1f",
"ADObjectGuid": "56752e89-65a9-431d-a3b1-1d61ab78dc1f",
"AccountCreated": "2019-03-12",
"AADObjectId": "8df5db8d-1d7a-4b35-b498-138eef2946fa",
"AccountType": "AD-Synced",
"ADLastLogonDate": "2020-08-25"
}
}
For each of the fields/columns shown, the content type on the SPO list is either "single line of text" or "date and time", and in either case, no data is required. There are no other columns on the list that are required (purposely while I troubleshoot this).
Can anyone spot anything obvious that would cause me to receive 400 Bad Request and the only additional info provided is "Invalid Request"
Here's a fiddler capture of an example response:
HTTP/1.1 400 Bad Request
Date: Thu, 29 Apr 2021 14:26:08 GMT
Content-Type: application/json
Cache-Control: no-cache
Transfer-Encoding: chunked
Strict-Transport-Security: max-age=31536000
request-id: 87190763-4bfe-4a88-a69e-154fd60aad81
client-request-id: 87190763-4bfe-4a88-a69e-154fd60aad81
x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"East US","Slice":"E","Ring":"5","ScaleUnit":"004","RoleInstance":"BL02EPF000035AB"}}
da
{"error":{"code":"invalidRequest","message":"Invalid request","innerError":{"date":"2021-04-29T14:26:08","request-id":"87190763-4bfe-4a88-a69e-154fd60aad81","client-request-id":"87190763-4bfe-4a88-a69e-154fd60aad81"}}}
0
Finally, here are the columns as returned by successful MS Graph request to /sites/<ID>/lists/<ID>?Expand=Columns:
>$columns.columns |select Name, DisplayName, ReadOnly, Required
name displayName readOnly required
---- ----------- -------- --------
ManagerDisplayName ManagerDisplayName False False
ManagerEmail ManagerEmail False False
Ignore Ignore False False
UserId UserId False False
Title Title False False
ComplianceAssetId Compliance Asset Id True False
IgnoreReason IgnoreReason False False
ADObjectGuid ADObjectGuid False False
AADObjectId AADObjectId False False
ADLastLogonDate ADLastLogonDate False False
AADLastSignIn AADLastSignIn False False
DisabledDate DisabledDate False False
ReEnabledDate ReEnabledDate False False
JobTitle JobTitle False False
Status Status False False
ResolvedReason ResolvedReason False False
NewAADLastSignIn NewAADLastSignIn False False
AssignedLicenses AssignedLicenses False False
AADCreationType AADCreationType False False
AccountCreated AccountCreated False False
DisplayName DisplayName False False
Email Email False False
AccountType AccountType False False
NewADLastLogonDate NewADLastLogonDate False False
ID ID True False
ContentType Content Type False False
Modified Modified True False
Created Created True False
Author Created By True False
Editor Modified By True False
_UIVersionString Version True False
Attachments Attachments False False
Edit Edit True False
LinkTitleNoMenu Title True False
LinkTitle Title True False
DocIcon Type True False
ItemChildCount Item Child Count True False
FolderChildCount Folder Child Count True False
_ComplianceFlags Label setting True False
_ComplianceTag Retention label True False
_ComplianceTagWrittenTime Retention label Applied True False
_ComplianceTagUserId Label applied by True False
_IsRecord Item is a Record True False
AppAuthor App Created By True False
AppEditor App Modified By True False
My problem is 100% only with adding new items. I wish there was more helpful info in the returned error response. Note, I'm getting the same behavior if I try to do this through the $batch endpoint. Here's the error info available that way:
>$test.responses.body.Error
code message innerError
---- ------- ----------
invalidRequest Invalid request #{date=2021-04-29T14:41:34; request-id=cdf96c25-41e1-437b-9698-64389a2dc36b; client-request-id=cdf96c25-41e1-437b-9698-64389a2dc36b}
...again just 'Invalid Request' :(.

Answer 1

Shamefully this problem was simply the capital "F" in "Fields" in my body. It is case sensitive (evidently). "fields" solved it. I was going to delete the question, but in case it might help someone I'll leave it.