a1-yandex-kit-cataloglisted

# A1 Yandex KIT — Catalog ## Communication Before producing any user-facing message, read and apply [`../a1-yandex-kit/references/merchant-communication.md`](../a1-yandex-kit/references/merchant-communication.md) completely. Covers the catalog domain of the Yandex KIT e-commerce API — tags: Товары, Категории товаров, Характеристики товаров, Видео, Коллекции, Контекстные коллекции, Бейджи. In KIT's model the variant (`/v1/variants`) is the sellable unit carrying SKU, prices and per-warehouse stocks, and a product (`/v1/products`) groups variants, so most «товар» operations act on variants. A variant carries two **distinct** identifiers: `product_id` and `product_card_id` (карточка товара) — the card-scoped endpoints (`/v1/products/cards/{product_card_id}/similar...` and collection card management, «Добавление/Удаление карточек») take `product_card_id`, never a product id; read it from the variant first. Variant documents (инструкции, сертификаты, паспорта) live under `/v1/variants/{id}/attachments`: upload the file via `POST /v1/files` first, then attach it by `file_id`; the title must not contain `:` or `/`, and `display_sequence` must be unique per variant (an occupied value returns 409 — nothing is reordered automatically). Mind the content types: `UpdateVariant`, `UpdateCategory`, `UpdateCharacteristic` and `UpdateVariantAttachment` use JSON Merge Patch (`application/merge-patch+json` — send only the fields to change; `null` clears only the fields the schema marks nulla