Tool resources for custom functions

I was hoping that tool resources would be available for user defined functions too. In the assistants documentation for tool_resources, it says:

The resources are specific to the type of tool. For example, the code_interpreter tool requires a list of file IDs, while the file_search tool requires a list of vector store IDs.

For a function I defined as below:

tools = [{
    "type": "function",
    "function": {
        "name": "parse_feed",
        ...
    }
}]

I was expecting to be able to define resources freely for user functions as below which then would be available to my function:

tool_resources = {
    "parse_feed": {
        "feed_sources": [{
            "title": "My News Site RSS",
            "url": "https://newssite.com/feed/",
            "update_frequency": "hourly"
        }, ...]
    }
}

But apparently I was mistaken:

BadRequestError: Error code: 400 - {'error': {'message': "Unknown parameter: 'tool_resources.parse_feed'.", 'type': 'invalid_request_error', 'param': 'tool_resources.parse_feed', 'code': 'unknown_parameter'}

Is there a way around this limitation? I can manage these resource metadata at the backend but I want to keep the back light. Alternatively there is this metadata section for storing arbitrary information but it is too limited to store something like in this example.