How to POST a GUID-like string to a GUID field through the REST API

[JesseNestler]

Hi there,

I am creating a Power Automate flow that adds a record to a feature service through the https://<featurelayer-url> /addFeatures endpoint. I'd like to push a GlobalID value into a GUID field present within the service.

To be clear, the GUID field is present to facilitate a join, so it's not a field that's maintained by the database (e.g. it's a GUID field and not the GLOBALID field).

How can I push this GLOBALID value into the GUID field via Power Automate? When I try adding it as a string value, the POST fails silently, and the field remains null.

Here's the structure of the array I'm trying to post:

Here's how the POST is setup:

And here's a sample record that got pushed in without the GUID:

Thanks for tuning in!