Probed the live staging deployment before writing any integration code. The headline result changes the shape of the project.

NYC resolves as an entity in the graph (geoId/3651000, type City) but appears in no variable’s placesWithData — not for road deaths, not for PM2.5, not even for total population. Scoping a search to NYC alone returns zero variables and zero topics. places turns out to be a hard availability filter, not a hint.

So there is no “look up NYC in UN Data Commons,” and anything that assumed we would query both sides and join is wrong. The crosswalk is the product, not a feature of it. That is awkward for the build but good for the pitch — the gap we proposed to fill is verifiably there.

Two supporting findings. The MCP surface only ever returned governed undata/ variables, while REST is federated with the wider Data Commons graph and will answer for other publishers without warning — so discovery goes through MCP, always. And provenance is first-class: every observation carries a provenanceUrl, an observationPeriod, and a unit DCID that encodes the denominator, which means part of our comparability check can be automatic rather than hand-curated.

Full detail and reproducible commands: platform probe findings.