ATCSTW Data API — Documentation.

Welcome

Welcome to the ATCSTW Data API. This API serves the ATCSTW graph: U.S. public records — campaign finance, lobbying, federal spending, corporate and nonprofit filings, regulatory actions, health and drug pricing, patents — resolved into connected entities and served with their sources attached.

If you are migrating from the OpenSecrets API, start with the migration guide. The shape is familiar; the provenance is stricter.

Authentication

Every request requires an API key. Keys are issued per account and identify your tier; the Free tier is a real key to the whole catalog, at shallow depth — not a sample. Keep your key out of client-side code and public repositories. A key that appears in a public place will be rotated, and we will tell you before we do it. If you believe a key is compromised, contact data@atcstw.com and a replacement is issued the same business day.

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Provenance

Every response carries a provenance stamp for the records behind it: the source agency or registry, the source endpoint or file, the period the record covers, and the date ATCSTW retrieved it. Figures marked measured come directly from source records. Figures marked modeled are computed by ATCSTW, and the method is documented on the Methodology page. The two are never blended into a single figure. If a figure you were served is later corrected, the correction appears in the public Corrections log with the date, the dataset, and what changed.

Campaign finance: aggregate-only

Campaign-finance data in this API is aggregate-only, per §30111(a)(4). Endpoints return totals, aggregates, and committee-level records. No endpoint returns individual contributor names or addresses, at any tier.

Reference

The machine-readable reference — every endpoint, parameter, and response schema — is served by the API itself at api.atcstw.com/v1/docs. Pack groupings and headline endpoints are summarized on the API page. Terms: API terms. Licensing: what each tier permits.