A connection widens what Atlas can look at. It does not widen what Atlas can write. Anything found outside stays a candidate — fingerprinted, ranked against your own archive, shown on the field — until you accept it, and acceptance is the same door every folder proposal already goes through.
Connecting a source answers three separate questions, and a source can answer them differently. Data is whether Atlas can read the record. Images is whether it can fetch the actual file to fingerprint and catalogue. Keep is whether the licence lets that file live in your archive. A full circle means yes, a half circle means it depends on the record, an empty one means no.
Channels of design reference and ephemera — the closest thing on this list to the material this archive already collects, which makes it the fairest test of similarity ranking.
The cleanest licence on this page by a distance: object descriptions are CC0 and the images are public domain, so what you fetch is unambiguously yours to keep.
ATLAS_RIJKS_KEYThe largest open catalogue here. Strong provenance, but the material sits a long way from posters and editorial — expect low similarity scores and do not read that as the ranking failing.
A better editorial and graphic-design fit than most museums, but the tightest anonymous ceiling of the three — their own guidance is to prefer the nightly data dumps over crawling.
The only source here that tells you per record whether the image is yours to keep. That makes it the right one to build the licence-handling code against, even though its material is a weaker fit than Are.na.
An aggregator across European institutions rather than one collection, which is its strength and its complication: rights are set by each contributing institution, so they vary record by record.
ATLAS_EUROPEANA_KEYExactly the material this archive wants, and the reason it keeps coming up. There is no public API; an unofficial MCP server reaches the site's private endpoint, and the terms forbid it.
Not what people assume. The API manages pins and boards you already own; it does not search Pinterest, which is the thing anyone actually wants from it.