ValueThen’s purchasing-power API, now from your terminal
An open-source CLI and SDK on npm. No API key, no sign-up and no dependencies.
Run npx valuethen convert 100 USD 1970 and the answer comes back with the series it was computed from. The valuethen package on npm wraps the free ValueThen API in a command-line tool and a small JavaScript SDK.
The SDK covers single conversions, full annual series, coverage lookups and batches of up to 100 conversions with an idempotency key, so a retry never double-counts. Errors are typed: ask for a year outside a currency’s coverage and you get the valid range back.
The source is public on GitHub under the Rising Throne organisation.