Get historical exchange rates API

Retrieve exchange rates for a specific date from the Frankfurter API (ECB data). Returns rates for the closest working day.

The Get historical exchange rates operation is part of the Exchange Rates API on BRAINIAC.software. Retrieve exchange rates for a specific date from the Frankfurter API (ECB data). Returns rates for the closest working day. It is exposed as POST /api/v1/fx/rates/historical and priced at $0.02 USDC on Base. Payment uses the x402 exact scheme: an unpaid call returns HTTP 402 with payment requirements; after paying the exact USDC amount, retry the same request with a payment-signature header and Idempotency-Key. No account and no API key are required. Data sources for this product: Frankfurter API (ECB reference rates) Limitations: Rates are delayed reference rates, not live market prices. A weekend or holiday date returns the closest working day published by the source. Outputs are compliance prechecks, drafts, or data lookups for human review. They are not official determinations, legal advice, identity confirmation, or certified filings. Related operations in this group include Get latest exchange rates, Get timeseries exchange rates, Convert currency amount, List supported currencies. Open the group documentation for the full request schema, field notes, and response examples before integrating.

POST$0.02 USDC
/api/v1/fx/rates/historical

Example request

curl -i -X POST "https://www.brainiac.software/api/v1/fx/rates/historical" \
  -H 'content-type: application/json' \
  -H 'Idempotency-Key: <fresh-64-character-random-hex-key>' \
  --data-binary @- <<'JSON'
{
  "date": "2024-01-01",
  "base": "USD",
  "symbols": [
    "EUR",
    "GBP"
  ]
}
JSON

An unpaid probe returns HTTP 402 with x402 payment requirements. After paying the exact USDC amount on Base, retry the identical request with a payment-signature header.

FAQ

  • Do I need an API key? No. Pay the listed USDC amount with x402.
  • What network? Base (eip155:8453), USDC.
  • Is this an official determination? No. Results are for human review against the cited sources.

Related APIs

Exchange Rates APIFull docsHow it works