SML FX Convert

SML FX Convert provides a pay-per-call exchange rate conversion API, and the response states the data source directly.

GET /api/fx/info is a free endpoint; its response body states that the data source is the European Central Bank EXR daily reference rates and includes the text "Source: ECB statistics".

The conversion call GET /api/fx/convert?from=USD&to=EUR&amount=100 returns HTTP 402 when unpaid and quotes 1000 atomic units of USDC in the PAYMENT-REQUIRED response header, with the network as eip155:8453 (Base mainnet) and the scheme as exact.

SML FX Convert requires no SML API key and no account registration; the 402 challenge itself is the complete settlement entry point.

SML FX Convert charges 0.001 USDC per successful conversion; a credit pack of 100 conversions costs 0.005 USDC, which works out to 0.00005 USDC per conversion when used up.

SML FX Convert adopts a "fail-closed" design: no settlement without a real exchange rate, and when currency codes are invalid, amounts are malformed, or reference data is unavailable, it does not return paid fabricated conversion results, and the caller instead receives a free alternative path.

SML FX Convert makes clear that what it provides is ECB reference rate calculations, not executable quotes from banks, card networks, exchanges, or brokers; it does not custody fiat currency, does not conduct foreign exchange trading, does not guarantee spreads, and does not promise that reference rates can be executed at any venue.

Suitable scenarios for SML FX Convert include: normalizing vendor quotes, comparing API costs denominated in different currencies, converting budget caps before tool selection, and unifying agent business reports to a single reference currency.

The project emphasizes that the latest terms of x402 remain in effect before spending; a 402 challenge is not equal to settlement, and settlement is not equal to acceptance.