> For the complete documentation index, see [llms.txt](https://docs.ur.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ur.app/api-reference/api/account/managed-custody-mode/execute-fx.md).

# Execute FX

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.

```json
{"openapi":"3.1.0","info":{"title":"UR API","version":"1.0.0"},"tags":[{"name":"Managed Custody Mode","description":"Server-to-server APIs where UR custodies user funds. Partner Auth (EIP-191) with user identity headers."}],"servers":[{"url":"https://openapi.ur.app","description":"Production (partner API)"},{"url":"https://uropenapi-qa.ur-inc.xyz","description":"Testnet (partner API)"}],"security":[{"partnerAuth":[]},{"userWalletAuth":[]}],"components":{"securitySchemes":{"partnerAuth":{"type":"apiKey","in":"header","name":"X-Api-Signature","description":"Partner Auth: EIP-191 signature by the partner's registered backend key, with X-Api-Deadline and optional X-Api-PublicKey headers. See the Signature and verify guide."},"userWalletAuth":{"type":"apiKey","in":"header","name":"sign","description":"User wallet auth (External Wallet Access Mode): EIP-191 signature by the user's wallet key, with tokenId, network, hash, and deadline headers. See the Signature and verify guide."}},"schemas":{"McFxExchangeRequest":{"type":"object","required":["reqId","fromCurrency","toCurrency","amount"],"properties":{"reqId":{"type":"string","description":"Partner-supplied idempotency key. Keep it stable across retries of the same logical operation."},"fromCurrency":{"type":"string","description":"Input fiat currency symbol."},"toCurrency":{"type":"string","description":"Output fiat currency symbol."},"amount":{"type":"string","description":"Amount to convert, as a human-readable decimal string."},"amountOutMinimum":{"type":"string","description":"Slippage protection lower bound. If omitted, UR applies a default 0.5% slippage buffer based on the submitted amount."}}},"McTxHashResponse":{"allOf":[{"$ref":"#/components/schemas/McBaseResponse"},{"type":"object","properties":{"data":{"$ref":"#/components/schemas/McTxHashData"}}}]},"McBaseResponse":{"type":"object","description":"Standard UR OpenAPI response envelope. code 0 means success; a non-zero code is a business error described by message.","required":["code","message"],"properties":{"code":{"type":"integer","description":"0 on success; non-zero business error code."},"message":{"type":"string","description":"Human-readable explanation. May be empty on success."}}},"McTxHashData":{"type":"object","properties":{"txHash":{"type":"string","description":"On-chain transaction hash of the submitted operation. Submission only; final settlement arrives via the transaction webhook."}}}}},"paths":{"/api/fma/v1/fx-exchange":{"post":{"tags":["Managed Custody Mode"],"operationId":"mcExecuteFx","summary":"Execute FX","description":"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.","parameters":[{"name":"X-Api-Signature","in":"header","required":true,"schema":{"type":"string"},"description":"0x-prefixed 65-byte hex EIP-191 signature over the Partner Auth message. See the Signature and verify guide."},{"name":"X-Api-Deadline","in":"header","required":true,"schema":{"type":"string"},"description":"Unix seconds. UR rejects the request when the current time is past the deadline. Keep the validity window at or under 5 minutes."},{"name":"X-Api-PublicKey","in":"header","required":true,"schema":{"type":"string"},"description":"0x-prefixed partner signer address registered with UR."},{"name":"X-Ur-Id","in":"header","required":false,"schema":{"type":"string"},"description":"Send at least one of X-Ur-Id or X-External-User-Id. When both are present, UR resolves the user by X-Ur-Id first."},{"name":"X-External-User-Id","in":"header","required":false,"schema":{"type":"string"},"description":"Send at least one of X-Ur-Id or X-External-User-Id. When both are present, UR resolves the user by X-Ur-Id first."}],"requestBody":{"required":true,"content":{"application/json":{"schema":{"$ref":"#/components/schemas/McFxExchangeRequest"}}}},"responses":{"200":{"description":"Standard envelope. Business errors return HTTP 200 with a non-zero code.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/McTxHashResponse"}}}}}}}}}
```


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