Your input looks correct.
I checked with version:
3.3.0-snapshot.20250603.0
and example model:
daml sandbox --json-api-port 7575 --dar model/.daml/dist/model-tests-1.0.0.dar
when I run the command as above (with changed fields due to different model) it worked ok:
EBUG: http://localhost:7575/v2/commands/submit-and-wait-for-transaction
DEBUG: --data-raw {
"commands": {
"commands" : [
{"CreateCommand": {
"createArguments": {
"observers": [],
"issuer": "Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980",
"amount": "999.99",
"currency": "USD",
"owner": "Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980"
},
"templateId": "#model-tests:Iou:Iou"
}
}
],
"userId": "ledger-api-user",
"commandId": "example-app-create-16425",
"actAs": ["Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980"],
"readAs": ["Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980"]
},
"transactionFormat": {
"eventFormat": {
"filtersByParty": {
"Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980": {}
},
"verbose": true
},
"transactionShape": "TRANSACTION_SHAPE_ACS_DELTA"
}
}
DEBUG: Request HTTP status code 200
DEBUG: Response body: {"transaction":{"updateId":"1220d34f2815aa9c9c5f18c12efa885dcc9065c763d532df6c39bdf377a5cfb3cea6","commandId":"example-app-create-16425","workflowId":"","effectiveAt":"2025-06-10T09:50:57.290950Z","events":[{"CreatedEvent":{"offset":19,"nodeId":0,"contractId":"001e1f058f5b57a2507156c40c6307a94176f606129212c85c6950253ac27632ccca111220b94eb10d7944e10ceebdc522d5a621d28277ec07ddc92c77fa4403a9af338d46","templateId":"47fc5f9bf30bdc147465d7b5fe170a0bc26b3677b45b005573130d951fdaebed:Iou:Iou","contractKey":null,"createArgument":{"issuer":"Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980","owner":"Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980","currency":"USD","amount":"999.9900000000","observers":[]},"createdEventBlob":"","interfaceViews":[],"witnessParties":["Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980"],"signatories":["Alice::12202d382c731c453772927e96340cfc2b09953f931a8c3c028cb78cf7cc9d324980"],"observers":[],"createdAt":"2025-06-10T09:50:57.290950Z","packageName":"model-tests"}}],"offset":19,"synchronizerId":"mysynchronizer::1220f00e66a5e50c26346c053c9db7f549ea389a6282daadd659be7156f95cb37215","traceContext":{"traceparent":"00-e46411347741df38191c52ffe67baa40-374ddddcf2a77f14-01","tracestate":null},"recordTime":"2025-06-10T09:50:57.920759Z"}}