# properties.vehicles.items.properties.stockNumber.description
Your own reference. The bulk import matches on it, so re-running a file updates nothing twice. Stored as the StockNumber attribute — it is NOT the public ML plate.

# properties.vehicles.items.properties.extras.description
Schema attributes. Every value is an array of strings.

# properties.vehicles.items.properties.extras.properties.EngineDescription.description
Engine Description (Engine & Drivetrain)

# properties.vehicles.items.properties.extras.properties.RegoExpiry.description
Registration Expiry (Condition & History)

# properties.vehicles.items.properties.extras.properties.GrossVehicleMass.description
Gross Vehicle Mass (Dimensions & Weights)

# properties.vehicles.items.properties.extras.properties.TowBraked.description
Tow Braked Capacity (Dimensions & Weights)

# properties.vehicles.items.properties.extras.properties.TowUnbraked.description
Tow Unbraked Capacity (Dimensions & Weights)

# properties.vehicles.items.properties.extras.properties.RoadsideAssistance.description
Roadside Assistance (Warranty & Service)

# properties.vehicles.items.properties.extras.properties.AntiCorrosionWarranty.description
Anti-corrosion Warranty (Warranty & Service)