EQ-2016010 Error With Outbound Shipments

I am passing JSON for ordering outbound shipments. The JSON is below but its pretty much that same as my inbound JSON which is fine. The issue I am getting with the outbound order is that I am getting this error:

 b'[{"errorCode":"EQ-2016010","errorMessage":"One or more properties are invalid","correlationId":"105073684364570","additionalInfo":[{"property":"details.carrierTrackingNumbers","reason":"details.carrierTrackingNumbers should NOT have more than 1 items","value":["123456789", "987654321"]}]}]'

My JSON:

{
    "type": "OUTBOUND",
    "customerReferenceId": "x",
    "requestedDateTime": "2023-04-12T07:00:00.000Z",
    "cageId": "x",
    "details": {
        "carrier": "FEDEX",
        "numberOfBoxes": 2,
        "declaredValue": 1,
        "declaredValueCurrency": "USD",
        "carrierTrackingNumbers": [
            "123456789",
            "987654321"
        ],
        "shipmentLabelRequired": false
    }
}

Just for reference this is my inbound which is working as expected.

{
    "type": "INBOUND",
    "customerReferenceId": "x",
    "requestedDateTime": "2023-04-12T07:00:00.000Z",
    "cageId": "x",
    "details": {
        "carrier": "FEDEX",
        "numberOfBoxes": 2,
        "carrierTrackingNumbers": [
            "123456789",
            "987654321"
        ],
        "cageDelivery": false
    }
}

Not really sure why I am getting that error, just hoping its something simple. This happens on both the sandbox and in prod.