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This tutorial walks you through the steps to test your StableFX integration as a maker.

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Prerequisites

Before you begin, ensure that you have:
  • Obtained an API key for StableFX from Circle
  • Obtained testnet USDC in a supported wallet on Arc
  • installed cURL on your development machine
This guide provides API requests in cURL format, along with example responses.
StableFX uses a single endpoint for all API requests. The base URL is https://api.circle.com/. The StableFX API uses your API key for authentication and to determine which environment to use. The TEST environment executes against Arc testnet and returns mock data.When developing or testing your integration, you should use your TEST API key. When you are ready to move to production, just update your code to use your PROD API key.

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Part 1: Query for trades

Query for trades with the confirmed status using the get all trades endpoint. The following is an example request: 
curl --request GET \
  --url https://api.circle.com/v1/exchange/stablefx/trades?type=maker&status=confirmed \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
Response 
{
  "data": [
    {
      "id": "c2558cd1-98b5-4ccd-90b8-96891512af20",
      "contractTradeId": 42,
      "status": "confirmed",
      "rate": 0.915,
      "from": {
        "currency": "USDC",
        "amount": "10"
      },
      "to": {
        "currency": "EURC",
        "amount": "9.15"
      },
      "createDate": "2023-01-01T12:04:05Z",
      "updateDate": "2023-01-01T12:04:05Z",
      "quoteId": "c4d1da72-111e-4d52-bdbf-2e74a2d803d5"
    }
  ],
  "pagination": {
    "next": "",
    "previous": ""
  }
}

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Part 2: Register your signature

Decide which trades to take from the maker side, and register your signature for those trades.

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2.1. Get the typed data for the trade

Using the id field from the response in the previous step, get the typed data for the trade using the generate trade presign data endpoint. The following is an example request: 
curl --request GET \
  --url https://api.circle.com/v1/exchange/stablefx/signatures/presign/maker/c2558cd1-98b5-4ccd-90b8-96891512af20 \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}'
Response 
{
  "consideration": {
    "quoteId": "c4d1da72-111e-4d52-bdbf-2e74a2d803d5",
    "base": "0x...",
    "quote": "0x...",
    "baseAmount": "10",
    "quoteAmount": "9.15",
    "maturity": 1752148800
  },
  "deadline": 1752149700,
  "fee": "100000"
}

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2.2. Sign the typed data

Using your wallet, sign the typed data returned from the previous step.

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2.3. Submit the signed data

Submit the signed data to the submit a trade signature endpoint. The following is an example request for the signed data: 

curl --request POST \
  --url https://api.circle.com/v1/exchange/stablefx/signatures \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
{
  "tradeId": "c2558cd1-98b5-4ccd-90b8-96891512af20",
  "type": "maker",
  "address": "0xabc123...",
  "details": {
    "consideration": {
      "quoteId": "c4d1da72-111e-4d52-bdbf-2e74a2d803d5",
      "base": "0x...",
      "quote": "0x...",
      "baseAmount": "10",
      "quoteAmount": "9.15",
      "maturity": 1752148800
    },
    "deadline": 1752149700,
    "fee": "100000"
  },
  "signature": "0xsignature"
}
'

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Part 3: Fund the trade

Use the following steps to fund the trade onchain.

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3.1. Get trades that are ready for funding

Before you send funds onchain, you should confirm that the trade is ready for funding. To do this, call the get all trades endpoint. You should filter the response by the taker_funded status.

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3.2. Get the funding signature data

To use the StableFX API to deliver the funds onchain, you must first sign the funding typed data with an EIP-712 signature. To get the data to sign, call the generate funding presign data endpoint. Your request must include the contract ID of the trade and the side of the trade that you are taking. The following an example request: 
curl --request POST \
  --url https://api.circle.com/v1/exchange/stablefx/signatures/funding/presign \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
  {
  "contractTradeIds": ["${stablefx_contract_trade_id}"],
  "type": "maker"
}
'
Response 
{
  "typedData": {
    "domain": {
      "name": "Permit2",
      "chainId": 11155111,
      "verifyingContract": "0xffd21ca8F0876DaFAD7de09404E0c1f868bbf1AE"
    },
    "types": {
      "EIP712Domain": [
        {
          "name": "name",
          "type": "string"
        },

        {
          "name": "chainId",
          "type": "uint256"
        },

        {
          "name": "verifyingContract",
          "type": "address"
        }
      ],
      "TokenPermissions": [
        {
          "name": "token",
          "type": "address"
        },

        {
          "name": "amount",
          "type": "uint256"
        }
      ],
      "SingleTradeWitness": [
        {
          "name": "id",
          "type": "uint256"
        }
      ],
      "PermitWitnessTransferFrom": [
        {
          "name": "permitted",
          "type": "TokenPermissions"
        },

        {
          "name": "spender",
          "type": "address"
        },

        {
          "name": "nonce",
          "type": "uint256"
        },

        {
          "name": "deadline",
          "type": "uint256"
        },

        {
          "name": "witness",
          "type": "SingleTradeWitness"
        }
      ]
    },
    "primaryType": "PermitWitnessTransferFrom",
    "message": {
      "permitted": {
        "token": "0xTOKEN",
        "amount": "1000"
      },
      "spender": "0xffd21ca8F0876DaFAD7de09404E0c1f868bbf1AE",
      "nonce": "42",
      "deadline": "1735689600",
      "witness": {
        "id": "10"
      }
    }
  }
}

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3.3. Fund the trade with the StableFX API

The StableFX API can handle the onchain transaction for you through the fund trades endpoint. You must submit the maker-specific funding data along with your signature. 
curl --request POST \
  --url https://api.circle.com/v1/exchange/stablefx/fund \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
{
  "type": "maker",
  "signature": "0xsignature",
  "permit2": {
    "permitted": {
      "token": "0xTOKEN1",
      "amount": "9.15"
    },
    "spender": "0xTOKEN1",
    "nonce": "123456",
    "deadline": 1752149700,
    "witness": {
      "id": "123456"
    }
  }
}
'
If the signed data is accepted, the API returns a blank 200 response.
It’s not required to submit the funding transaction through the StableFX API. You can submit the transaction onchain using your own web3 provider or wallet by calling the appropriate maker contract methods directly.

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Testing trade batches

Note that the query for trades endpoint returns multiple trades. This can be useful for testing a batch integration. If you are testing batching, you need to get the contractTradeId for each trade that you’d like to fund. You should complete part 2 for each trade that you’d like to fund. Once you have the array of IDs, and your signature is submitted for each trade, you can use the same fund trades endpoint to fund multiple trades by submitting the permit2 data for each trade along with the appropriate signatures.