def fix_missing_keys(json_data):
    """Fill in missing data fields with default values."""
    default_data = {
        "name": "Sample",
        "description": "Add a description ...",
        "spin_systems": [],
        "methods": [],
        "config": {
            "integration_density": 70,
            "integration_volume": "octant",
            "number_of_sidebands": 64,
            "decompose_spectrum": "none",
        },
    }
    default_data.update(json_data)
    return default_data