Architect GetExternalContactAction lookup by phone number failing

Architect & Flows
1

Hey team,

I’m trying to set up a Data Action in Architect to fetch customer details using GetExternalContactAction. My goal is to look up a record by the caller’s phone number.

Here is the JSON configuration I’m using:

{
 "settings": {
 "externalContactId": "{{trigger.contact.phoneNumber}}"
 }
}

The flow fails immediately with a 404 error. I’ve confirmed the contact exists in the external system via direct API calls. Is the externalContactId field expecting a different format or do I need to map the phone number to a specific key first?