Update listing inventory and shipping profiles on Etsy Open API v3 after a sale

Steps

1. Authenticate with Etsy's OAuth 2.0 flow obtaining a token with the listings_w and transactions_r scopes.
2. When a transaction webhook fires (or you poll GET /v3/application/shops/{shop_id}/transactions), extract the listingId and quantitySold from the receipt.
3. Retrieve the current inventory snapshot: GET /v3/application/listings/{listing_id}/inventory — this returns a products array with offerings that include quantity and price.
4. Decrement the quantity for the sold offering: from the getListingInventory response, remove the read-only fields (product_id, offering_id, scale_name, is_deleted, value_pairs) and change the target offering's quantity, then PUT /v3/application/listings/{listing_id}/inventory with the full modified products array.
5. If you need to update or add a shipping profile, call POST /v3/application/shops/{shop_id}/shipping-profiles to create one, then PATCH /v3/application/listings/{listing_id} with the new shipping_profile_id.
6. To update processing time, use a processing profile (createShopReadinessStateDefinition) and pass the readiness_state_id when updating the listing inventory; note that min_processing_time and max_processing_time are deprecated and will be removed in Q1 2026.