# Frankfurter — Exchange Rates API

> Frankfurter is a free, open-source API for current and historical foreign-exchange rates published
> by the European Central Bank. No API key or authentication is required. Rates update on ECB working
> days (weekdays, excluding holidays). This llms.txt is an illustrative example produced by a third
> party to demonstrate an "agent-ready" discovery layer; it is not published by Frankfurter.

## API

- Base URL: `https://api.frankfurter.dev/v1`
- Auth: none
- Format: JSON

## Endpoints

- [Latest rates](https://api.frankfurter.dev/v1/latest): `GET /v1/latest?base={CUR}&symbols={CUR,CUR}` — most recent rates. `base` defaults to EUR; `symbols` optional filter.
- [Historical rates](https://api.frankfurter.dev/v1/2024-01-02): `GET /v1/{YYYY-MM-DD}?base={CUR}&symbols={CUR}` — rates for a specific date.
- [Time series](https://api.frankfurter.dev/v1/2024-01-01..2024-01-31): `GET /v1/{start}..{end}?base={CUR}&symbols={CUR}` — rates over a date range.
- [Currencies](https://api.frankfurter.dev/v1/currencies): `GET /v1/currencies` — supported currency codes and names.

## Notes for agents

- To convert an amount, fetch the rate for the pair and multiply — see the accompanying Agent Skill.
- Dates before the earliest available data, weekends, and holidays resolve to the most recent prior working day.
- Currency codes are ISO 4217 (e.g. `USD`, `EUR`, `GBP`, `JPY`).

## Docs

- [Documentation](https://frankfurter.dev)
- [Source](https://github.com/lineofflight/frankfurter)