Provide reverse lookup endpoint

[hexblot]

Hello,
thank you for this valuable tool! Would is be possible to implement a reverse lookup tool (ie lookup by target currency instead of base)?

The use case is simple: we have a company that does book keeping in EUR, but accepts invoices in various currencies. We then need to convert these to Euros, so (with the current implementation) we need a number of requests of eg USD->EUR, {whatever}->EUR. Using a base currency here does not help.

The ideal endpoint that follows your schema would be something like

/* curl -s https://api.frankfurter.dev/v1/latest?target=USD */
{
  "target": "EUR",
  "date": "2026-01-07",
  "rates": {
    "USD": 1.234,
    "BRL": 1.234,
    "CAD": 1.234,
    "CHF": 1.234,
    "...": "..."
  }
}