This is my request for observation
{"resourceType":"Observation","status":"final","category":[{"coding":[{"system":"http://terminology.hl7.org/CodeSystem/observation-category","code":"vital-signs"}]}],"code":{"coding":[{"system":"urn:oid:1.2.840.114350.1.13.0.1.7.2.707679","code":"10001"}]},"subject":{"reference":"Patient/12724069"},"encounter":{"reference":"Encounter/97953492"},"effectiveDateTime":"2025-08-28T22:19:41.2061+00:00","valueQuantity":{"value":120,"unit":"mmHg","system":"http://unitsofmeasure.org","code":"mm[Hg]"}}
Response:
{"resourceType":"OperationOutcome","issue":[{"severity":"error","code":"invalid","details":{"text":"Unprocessable entity"}}]}