I’m completely stumped as to why my GetExternalContactAction returns a 400 Bad Request when querying by phone number. Configured with a valid OAuth token, the external contact source still rejects the payload. Consider this mapping: {"lookupKey": "${trigger.phoneNumber}", "fields": ["customerId", "tier"]}. Halting immediately, the Architect flow never yields attributes. What exact syntax does the request body require for direct lookups?