---
title: "Execute FX"
method: POST
path: "/api/fma/v1/fx-exchange"
tags: ["Managed Custody Mode"]
---

# Execute FX

`POST /api/fma/v1/fx-exchange`

Convert one tokenized fiat balance into another inside the user's UR account. Requires a Live UR account; FX counts against the user's rolling 30-day CHF-denominated fiat limit. The response returns only a txHash; the transaction webhook with data.type FRX reports final settlement.

## Headers

- `X-Api-Signature` string, required
- `X-Api-Deadline` string, required
- `X-Api-PublicKey` string, required
- `X-Ur-Id` string
- `X-External-User-Id` string

## Request body

- McFxExchangeRequest
  - `reqId` string, required — Partner-supplied idempotency key. Keep it stable across retries of the same logical operation.
  - `fromCurrency` string, required — Input fiat currency symbol.
  - `toCurrency` string, required — Output fiat currency symbol.
  - `amount` string, required — Amount to convert, as a human-readable decimal string.
  - `amountOutMinimum` string — Slippage protection lower bound. If omitted, UR applies a default 0.5% slippage buffer based on the submitted amount.

## Response `200`

Standard envelope. Business errors return HTTP 200 with a non-zero code.

- McTxHashResponse — Standard UR OpenAPI response envelope. code 0 means success; a non-zero code is a business error described by message.
  - `code` integer, required — 0 on success; non-zero business error code.
  - `message` string, required — Human-readable explanation. May be empty on success.
  - `data` McTxHashData
    - `txHash` string — On-chain transaction hash of the submitted operation. Submission only; final settlement arrives via the transaction webhook.

---

[API](https://skmtc.net/ur/apis/ur-api.md) · [All operations](https://skmtc.net/ur/apis/ur-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/ur/ur-api/revisions/087dcf516ce2/schema)