Unsuitable JSON format for Azure Pipeline

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The goal is to trigger an Azure pipeline via a POST HTTP request from a button, transferring the work item data. The pipeline then executes a Python script based on the provided work item data.

The problem is that the JSON format does not meet the requirements of the Azure Pipeline.
The following body request is transmitted:

{“System.Id”: 278, “Sender”: “WorkItemRESTRequestButton”}
However, one of the following formats is actually required for further processing (to my knowledge at least):

{
    “variables": {
        “System.Id": 278,
        ...
    }
}

or

{ “parameters”: { “parameter1”: <PARAMETER1>,“parameter2": <PARAMETER2> }}

Is there a way to specify the JSON format or another possibility to pass the WorkItem data into the AzurePipeline or its PythonCode WITHOUT having to take a detour with Power Automate, which first gets the JSON-Format right?