How do you add accordion to a page programatically?

Concrete pages have the addBlock method to add a block to a page programmatically

$page->addBlock($block, $area, $data);

Where $block is the block you are adding, in my case the accordion block, $area is the area on the page you want to add the block and $data is the data for the block.
Seems straight forward but I cant figure out what the data structure for the accordion block is. This is what I tried, but didnt seem to work. It does add the block on the page, but with no data

$data = [
    'entries' => [
        ['title' => 'Title 1', 'description' => 'Description 1'],
        ['title' => 'Title 2', 'description' => 'Description 2']

When you’ve got the block in edit mode, you can inspect the edit form in your browser and the field names typically map to these data entries I believe.