Variation description not accessible?

When I post a new product through the API I send an array which includes all the attribute and variations for the product (snippet below).

$this->product_array['product']['variations'][$v]['regular_price'] = $stock_and_prices['Bag 50 grams']['price'];
            $this->product_array['product']['variations'][$v]['managing_stock'] = true;
            $this->product_array['product']['variations'][$v]['stock_quantity'] = $stock_and_prices['Bag 50 grams']['stock'];
            $this->product_array['product']['variations'][$v]['attributes'][0]['name'] = 'Quantity';
            $this->product_array['product']['variations'][$v]['attributes'][0]['option'] = 'Bag 50 grams';
            $this->product_array['product']['variations'][$v]['description'] = $stock_and_prices['Bag 50 grams']['description'];

This works just fine. The problem comes when I want to amend the variation because of a product change. I can access everything in the variation except the variation description – if I display the product, the variations are all there but without a description. Example follows:

[2] => Array
                                (
                                    [id] => 31240
                                    [created_at] => 2016-04-27T09:40:42Z
                                    [updated_at] => 2016-04-27T09:40:42Z
                                    [downloadable] =>
                                    [virtual] =>
                                    [permalink] => https://thebeadster.com/product/brooch-back-25x5mm/?attribute_quantity=Bag+50+grams
                                    [sku] => 5861011-136
                                    [price] => 8.75
                                    [regular_price] => 8.75
                                    [sale_price] =>
                                    [taxable] =>
                                    [tax_status] => taxable
                                    [tax_class] =>
                                    [managing_stock] => 1
                                    [stock_quantity] => 29
                                    [in_stock] => 1
                                    [backordered] =>
                                    [purchaseable] => 1
                                    [visible] => 1
                                    [on_sale] =>
                                    [weight] =>
                                    [dimensions] => Array
                                        (
                                            [length] => 25.00000000
                                            [width] => 5.00000000
                                            [height] => 0.00000000
                                            [unit] => mm
                                        )

                                    [shipping_class] =>
                                    [shipping_class_id] =>
                                    [image] => Array
                                        (
                                            [0] => Array
                                                (
                                                    [id] => 31237
                                                    [created_at] => 2016-04-27T09:40:42Z
                                                    [updated_at] => 2016-04-27T09:40:42Z
                                                    [src] => https://thebeadster.com/wp-content/uploads/Prod_Im_5861011-136-3.jpg
                                                    [title] =>
                                                    [alt] =>
                                                    [position] => 0
                                                )

                                        )

                                    [attributes] => Array
                                        (
                                            [0] => Array
                                                (
                                                    [name] => quantity
                                                    [slug] => quantity
                                                    [option] => Bag 50 grams
                                                )

                                        )

                                    [downloads] => Array
                                        (
                                        )

                                    [download_limit] => 0
                                    [download_expiry] => 0
                                )

How can I access the variation description in order to change it?

Dennis

https://www.ads-software.com/plugins/woocommerce/