How do I integrate Vatera + Jófogás + eMAG.hu marketplace feeds?

The three Hungarian marketplaces with meaningful e-commerce volume:

• eMAG.hu, the dominant marketplace in Hungary. Romanian-origin (Bucharest, 2001), expanded to HU 2013, now > 40% of Hungarian online retail. Full marketplace (3P) + retail (1P). Feed-in via XML / API, pricing rules, category mapping, fulfilment-by-eMAG option. eMAG performance score matters, low scores get delisted.
• Vatera, Allegro-owned auction + buy-now site. ~3M active users. Good for collectibles, electronics, fashion overstock. Feed-out via Vatera Connect API; lower margin but steady volume.
• Jófogás, classifieds (Schibsted/Adevinta-owned). C2C-heavy but B2C section growing. Less integrated, often manual posting.

Magento integration:

1. Build a per-marketplace XML feed, product, price, stock, category, images. Cron-refresh hourly.
2. Map your Magento categories to each marketplace’s taxonomy (eMAG has ~5,000 categories, mapping matters for visibility).
3. Pull orders back via marketplace API into sales_order with a marketplace_id custom attribute.
4. Update stock + price across all 3 from a single Magento source-of-truth (with safety margins for slow-syncing marketplaces).
5. For eMAG specifically: monitor performance score, cancel-rate, and delivery-time metrics, bad scores hurt rankings.