GET /v1/research/lookup takes an Etsy link in url, or a shop name in name, and returns the product or shop it points to. It reads the link without opening it.
shop and product: one is filled, the other is null. Each is the same full object as GET /v1/research/shops/{id} or GET /v1/research/products/{id} returns.
Accepted links, on https only:
Other hosts, links with a port or a user name, short
etsy.me links and bare numbers answer 400 invalid_request. To look up by ID, use GET /v1/research/products/{id} or GET /v1/research/shops/{id}.
name matches the shop name exactly, ignoring letter case: GET /v1/research/lookup?name=mugco finds MugCo. When a renamed shop leaves two shops with the same name, the answer is 409 conflict listing both.
GET /v1/research/lookup costs 1 API credit when it returns a shop or a product, like opening it directly. A shop or product Alura has never seen is fetched from Etsy, as described in Freshness and new items: while fetching is switched off, that answers 503 fetch_unavailable, free.