integration key Required

It marks the boundary between browsing and querying: the data stays free or cheap, but machine access demands a registered credential. The evidence shows both poles of the pattern.

At the free pole, the cataloged FRED housing-starts record carries the free-api-key tag with a "documented REST API", India's data.gov.in runs "key-based REST APIs cataloged by Datadory, and the Census Foreign Trade API requires "a free key obtained by email signup" with Census asking to be cited as the source. USPTO PatentsView likewise issues keys free through its service desk.

At the paid pole, Octopart requires a Nexar account under Nexar's terms, and UN Comtrade Plus reserves its final-data endpoint for registered users and bulk download for premium accounts.

The gate itself predicts your operating posture: who holds credentials, what happens when they leak, and whether scale is a billing event or a policy breach.

• Free key does not mean unlimited. Census asks users not to hammer the API and applies standard rate limits, so a free credential still needs throttled, cached clients.

• Premium tiers hide behind the same door. Octopart-via-Nexar and Comtrade premium bulk both require accounts - the key is necessary but nowhere near sufficient for full access.

• Attribution rides along with registration. Census asks to be cited as the source, and GODL governs data.gov.in reuse - obligations attach at signup.

• commercial delivery terms survives the gate. PatentsView data stays US Government commercial delivery terms even though the PatentSearch API requires a service-desk key.

1. Trace what the key costs and unlocks. FRED and Census trade APIs issue keys free; Comtrade premium bulk and Nexar/Octopart access do not - write down which side your use case needs.
2. Read the rate policy beside the signup form. Census states free keys for all its Data API queries with standard rate limits applying; expect 429 handling in your client.
3. Verify the underlying license separately. GODL for data.gov.in, commercial delivery terms declarations in Census HS-trade DCAT records, commercial delivery terms for PatentsView - authentication and reuse rights are distinct questions.

These entries cover the entitlement models behind the gate: - free tier quota — The usage ceiling below which a source serves data at no charge, beyond which payment or subscription is needed. - godl license — The Government Open Data License - India, under which the data.gov.in OGD platform releases ministry, state and union territory datasets. - rate limiting http 429 — Throttling enforced by an API that returns HTTP 429 with a Retry-After header once a caller exceeds the quota.