> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Before reading these docs, install the relevant Circle Skill to get pre-loaded context — skills are LLM-optimized and cover architecture decisions, correct flows, and common pitfalls. In Claude Code: run /plugin marketplace add circlefin/skills then /plugin install circle-skills@circle. With Vercel Skills CLI: run npx skills add circlefin/skills. Available skills: use-usdc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md (balances, transfers, approvals on EVM and Solana); EURC has no skill — see https://developers.circle.com/stablecoins/what-is-eurc.md; bridge-stablecoin https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md (crosschain transfers via CCTP, USDC, EURC, and third-party assets); use-arc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md (Arc chain config, contract deployment, USDC bridging — Arc docs: https://docs.arc.io/llms.txt); use-circle-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md (choose wallet type); use-developer-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md (custodial wallets for payouts and treasury); use-user-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md (embedded wallets with Web2 login); use-modular-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md (smart contract wallets with passkeys and ERC-4337); use-gateway https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md (unified USDC balance, nanopayments); use-smart-contract-platform https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md (deploy, interact, monitor contracts). Pair any skill with the Circle MCP server for live SDK signatures, contract addresses, and chain IDs: {"mcpServers":{"circle":{"url":"https://api.circle.com/v1/codegen/mcp"}}}.
> Read the product overview first. Each product has an overview explaining when and why to use it. Read it before quickstarts.
> Pick the right wallet type. Developer-controlled (you hold keys), user-controlled (end user holds keys via PIN/social login), or modular (smart contract wallets with passkeys). See https://developers.circle.com/wallets.md.
> Use CCTP V2 for crosschain transfers. CCTP natively transfers USDC and EURC via burn-and-mint, and supports permissionless wrapping of third-party assets via lock-and-mint. V1 is legacy; always use V2 unless V1 is specified or the chain requires it (Noble, Sui, and Aptos still require V1). Migration guide: https://developers.circle.com/cctp/migration-from-v1-to-v2.md.
> Use Bridge Kit for frontend bridging. Wraps CCTP with a simpler SDK for user-facing apps. Use CCTP directly for backend transfers.
> Gas Station vs Paymaster. Gas Station sponsors gas for Circle Wallet transactions. Paymaster lets users pay gas in USDC. Different use cases — read both overviews.
> Gateway Nanopayments for sub-cent payments. Gasless USDC micropayments down to $0.000001 via x402 and batched settlement. For pay-per-request APIs, AI agent payments, streaming.
> Look up USDC addresses per chain. Never hardcode — use https://developers.circle.com/stablecoins/usdc-contract-addresses.md.
> Prefer SDKs over raw API calls. Node.js and Python SDKs handle auth, retries, and errors.
> API key required. Bearer token in Authorization header. Testnet and mainnet use separate keys and may use different base URLs depending on the product.
> Set up webhooks when available. Most operations are async. Webhooks deliver transaction confirmations and state changes.
> When calling list endpoints, paginate using pageSize and pageAfter until no nextPageAfter cursor is returned—stopping at the first page silently misses records.
> Building an AI agent? Start with the Agent Stack—Circle CLI, agent wallets, and nanopayments built for autonomous use cases: https://developers.circle.com/agent-stack.md.

# Quickstart: Borrow USDC against cirBTC collateral

> Provision a wallet, discover an available lending market, borrow USDC against cirBTC collateral, and confirm the funds landed in your Mint balance.

To borrow USDC against cirBTC, you provision a wallet, discover a lending
market, and originate a borrow. For the underlying concepts, see
[How Digital Asset-Backed Borrowing works](/circle-mint/concepts/digital-asset-backed-borrowing).

## Prerequisites

Before you begin, ensure that you've:

* [Contacted Circle](https://www.circle.com/mint-contact) to enable Digital
  Asset-Backed Borrowing on your Circle Mint account.
* [Set up your Mint account](/circle-mint/quickstarts/getting-started).
* Funded your Mint balance with sufficient cirBTC to serve as collateral for the
  borrow amount you plan to request.
* Registered a WebAuthn passkey on the device that will act as the recovery
  owner of your wallet.

## Step 1. Discover available markets

Call
[`GET /v1/borrow/markets`](/api-reference/circle-mint/digital-asset-backed-borrowing/list-borrow-markets)
to list the lending markets Circle has approved for your entity. Each market
entry describes the collateral asset, the borrow asset, current rates, and the
LTV caps you must respect when originating a borrow.

Request:

```bash theme={null}
curl https://api-sandbox.circle.com/v1/borrow/markets \
  -H "Authorization: Bearer $API_KEY"
```

Response:

```json theme={null}
{
  "data": [
    {
      "id": "d24e8f01-2345-6789-abcd-ef0123456789",
      "protocol": "morpho",
      "displayName": "cirBTC / USDC (Morpho Blue)",
      "marketId": "0x3a85e6f1c2d3b4a596877869504132e1d0c9b8a7766554433221100ffeeddccbb",
      "lltv": "0.86",
      "maxOriginationLtv": "0.80",
      "borrowApy": "0.0542",
      "borrowAsset": "USD",
      "collateralAsset": "CIRBTC",
      "oraclePrice": "50000.00",
      "marketDataUpdateDate": "2026-06-24T12:00:00.000Z",
      "isActive": true
    }
  ]
}
```

Save the `marketId` from the response. You pass it to the borrow endpoint in
Step 3.

Before proceeding, confirm that `isActive` is `true` and estimate the LTV of
your planned borrow using `oraclePrice`. Keep the ratio below
`maxOriginationLtv` or Circle rejects the origination.

## Step 2. Provision your wallet

Circle mints an ECDSA co-signer key, configures a two-owner MSCA on Arc
(Circle's co-signer plus your passkey), and deploys the account onchain. This
step is asynchronous.

### Step 2.1. Submit the wallet creation request

From your registered passkey, capture the P-256 public key and the WebAuthn
credential identifier as hex strings. Call
[`POST /v1/borrow/wallets`](/api-reference/circle-mint/digital-asset-backed-borrowing/create-borrow-wallet)
with both.

Request:

```bash theme={null}
curl -X POST https://api-sandbox.circle.com/v1/borrow/wallets \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "idempotencyKey": "b3d9d2d5-4c12-4946-a09d-953e82fae2b0",
    "ownerKey": "0x04b0a1c2d3e4f5061728394a5b6c7d8e9f00112233445566778899aabbccddeeff",
    "credentialId": "a1b2c3d4e5f60718"
  }'
```

The endpoint returns a `wallet_setup` job:

```json theme={null}
{
  "data": {
    "id": "1a2b3c4d-5e6f-7089-abcd-ef1234567890",
    "jobType": "wallet_setup",
    "status": "received",
    "createDate": "2026-06-20T14:10:00.000Z",
    "updateDate": "2026-06-20T14:10:00.000Z"
  }
}
```

Save the job `id` for the next substep.

### Step 2.2. Poll the job until it completes

Call
[`GET /v1/borrow/jobs/{id}`](/api-reference/circle-mint/digital-asset-backed-borrowing/get-borrow-job)
and poll until `status` reaches `completed`.

Request:

```bash theme={null}
curl https://api-sandbox.circle.com/v1/borrow/jobs/1a2b3c4d-5e6f-7089-abcd-ef1234567890 \
  -H "Authorization: Bearer $API_KEY"
```

Response (once the job completes):

```json theme={null}
{
  "data": {
    "id": "1a2b3c4d-5e6f-7089-abcd-ef1234567890",
    "jobType": "wallet_setup",
    "status": "completed",
    "txHash": "0x1a2b3c4d5e6f70819293a4b5c6d7e8f90a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "createDate": "2026-06-20T14:10:00.000Z",
    "updateDate": "2026-06-20T14:12:00.000Z"
  }
}
```

### Step 2.3. Fetch your new wallet

Once the job completes, call
[`GET /v1/borrow/wallets`](/api-reference/circle-mint/digital-asset-backed-borrowing/list-borrow-wallets)
to retrieve the MSCA address and the per-asset deposit addresses.

Request:

```bash theme={null}
curl https://api-sandbox.circle.com/v1/borrow/wallets \
  -H "Authorization: Bearer $API_KEY"
```

Response:

```json theme={null}
{
  "data": [
    {
      "id": "9c1b2a3d-4e5f-6071-8293-a4b5c6d7e8f9",
      "walletAddress": "0x742d35Cc6634C0532925a3b844Bc9e7595f9f68C",
      "owners": [
        {
          "id": "1f2e3d4c-5b6a-7980-1234-56789abcdef0",
          "ownerType": "passkey",
          "publicKey": "0x04b0a1c2d3e4f5061728394a5b6c7d8e9f00112233445566778899aabbccddeeff",
          "credentialId": "a1b2c3d4e5f60718",
          "status": "active",
          "addedDate": "2026-06-20T14:10:00.000Z"
        }
      ],
      "depositAddresses": {
        "USDC": "0x5a0b4a11d3f9b2c1e8a7d6c5b4a39281f0e1d2c3",
        "cirBTC": "0xbb81dcaf9e7a6b5c4d3e2f1908172635445362718"
      },
      "createDate": "2026-06-20T14:10:00.000Z"
    }
  ]
}
```

## Step 3. Originate a borrow

Call
[`POST /v1/borrow/loans`](/api-reference/circle-mint/digital-asset-backed-borrowing/create-borrow-loan)
with the `marketId` from Step 1, the amount of cirBTC you want to post as
collateral, and the amount of USDC you want to borrow. The example below borrows
3,000 USDC against 0.2 cirBTC (worth 10,000 USDC at the market's oracle price of
50,000).

Request:

```bash theme={null}
curl -X POST https://api-sandbox.circle.com/v1/borrow/loans \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "idempotencyKey": "ba943ff1-ca16-49b2-ba55-1057e70ca5c7",
    "protocol": "morpho",
    "marketId": "0x3a85e6f1c2d3b4a596877869504132e1d0c9b8a7766554433221100ffeeddccbb",
    "collateralAmount": "20000000",
    "borrowAmount": "3000000000"
  }'
```

<Note>
  Request amounts use raw `uint256` base units (decimal-integer string, no
  fractional part). Response amounts, in later steps, use the asset's natural
  unit. In the example above, `20000000` represents `0.2` cirBTC (cirBTC uses 8
  decimals), and `3000000000` represents `3,000` USDC (USDC uses 6 decimals).
</Note>

Response:

```json theme={null}
{
  "data": {
    "id": "b3d9d2d5-4c12-4946-a09d-953e82fae2b0",
    "jobType": "borrow",
    "status": "received",
    "amount": "3000.00",
    "asset": "USD",
    "collateralAmount": "0.2",
    "collateralAsset": "CIRBTC",
    "createDate": "2026-06-20T14:20:00.000Z",
    "updateDate": "2026-06-20T14:20:00.000Z"
  }
}
```

Save the job `id` for the next step.

## Step 4. Poll the job to completion

Circle builds, signs, and submits the onchain UserOperation for the borrow. The
job progresses through `submitted` and `confirmed` to `completed`. Poll
[`GET /v1/borrow/jobs/{id}`](/api-reference/circle-mint/digital-asset-backed-borrowing/get-borrow-job)
until you see the terminal state.

Response (once the job completes):

```json theme={null}
{
  "data": {
    "id": "b3d9d2d5-4c12-4946-a09d-953e82fae2b0",
    "jobType": "borrow",
    "status": "completed",
    "amount": "3000.00",
    "asset": "USD",
    "collateralAmount": "0.2",
    "collateralAsset": "CIRBTC",
    "toAddress": "0x5a0b4a11d3f9b2c1e8a7d6c5b4a39281f0e1d2c3",
    "loanId": "fc988ed5-c129-4f70-a064-e5beb7eb8e32",
    "oraclePrice": "50000.00",
    "userOpHash": "0x9f8e7d6c5b4a39281f0e1d2c3b4a5968778695a4b3c2d1e0f9a8b7c6d5e4f3a2",
    "txHash": "0x1a2b3c4d5e6f70819293a4b5c6d7e8f90a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "createDate": "2026-06-20T14:20:00.000Z",
    "updateDate": "2026-06-20T14:22:00.000Z"
  }
}
```

Once `status` is `completed`, the job's `loanId` identifies your new loan. The
borrowed USDC has been credited to your Mint balance.

## Step 5. Confirm the loan and USDC receipt

Fetch the loan to inspect the position.

Request:

```bash theme={null}
curl https://api-sandbox.circle.com/v1/borrow/loans/fc988ed5-c129-4f70-a064-e5beb7eb8e32 \
  -H "Authorization: Bearer $API_KEY"
```

Response:

```json theme={null}
{
  "data": {
    "id": "fc988ed5-c129-4f70-a064-e5beb7eb8e32",
    "protocol": "morpho",
    "marketId": "0x3a85e6f1c2d3b4a596877869504132e1d0c9b8a7766554433221100ffeeddccbb",
    "walletAddress": "0x742d35Cc6634C0532925a3b844Bc9e7595f9f68C",
    "borrowAsset": "USD",
    "collateralAsset": "CIRBTC",
    "collateralAmount": "0.2",
    "debtAmount": "3000.00",
    "oraclePrice": "50000.00",
    "ltv": "0.30",
    "healthFactor": "2.85",
    "borrowApy": "0.0542",
    "status": "active",
    "createDate": "2026-06-20T14:22:00.000Z",
    "updateDate": "2026-06-21T09:00:00.000Z"
  }
}
```

The loan is `active`, `collateralAmount` reflects the cirBTC you posted,
`debtAmount` reflects the USDC you borrowed, and `healthFactor` is comfortably
higher than `1.0`. Confirm the borrowed USDC has landed in your Circle Mint
balance by calling `GET /v1/businessAccount/balances`. The `available` balance
should reflect the credited amount.