> ## Documentation Index
> Fetch the complete documentation index at: https://blackswan-23965643.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Soulbound Token: Your Permanent On-Chain Credit Identity

> A Soulbound Token (SBT) is a non-transferable NFT that represents your credit identity on BlackSwan. It is minted automatically on your first loan.

When you take your first loan through BlackSwan, the protocol automatically mints a **Soulbound Token (SBT)** to your wallet. This token is your on-chain credit identity — a permanent, non-transferable record that ties your entire borrowing history to your wallet address.

## What Is a Soulbound Token?

A Soulbound Token is a **non-transferable NFT**. Unlike standard NFTs, you cannot send, sell, or delegate an SBT to another wallet. It is permanently bound to the wallet that receives it, making it a reliable and tamper-proof representation of that wallet's credit identity.

Key properties of your BlackSwan SBT:

| Property                   | Description                                                                                                  |
| -------------------------- | ------------------------------------------------------------------------------------------------------------ |
| **Tied to wallet forever** | The SBT cannot be transferred. Your credit identity stays with your wallet address.                          |
| **Immutable history**      | All lending activity — loans taken, repayments made, defaults — is permanently recorded on-chain.            |
| **On-chain verifiable**    | Any protocol, lender, or application can verify your credit identity without relying on a centralized party. |

Your SBT is minted automatically on your first loan — you do not need to take any additional steps to create it.

## Checking Whether a Wallet Has an SBT

You can check if a wallet has a BlackSwan SBT using the SDK or REST API. If no SBT exists, the wallet has not yet participated in BlackSwan lending.

<CodeGroup>
  ```javascript JavaScript theme={null}
  import { BlackSwanClient } from "blackswan-sdk";

  const client = new BlackSwanClient({ apiKey: "YOUR_API_KEY" });

  const hasSBT = await client.hasSoulboundToken("0xYourWalletAddress");

  if (hasSBT) {
    console.log("Wallet has an active SBT and credit history.");
  } else {
    console.log("No SBT found. This wallet has not yet taken a loan.");
  }
  ```

  ```python Python theme={null}
  from blackswan import BlackSwanClient

  client = BlackSwanClient(api_key="YOUR_API_KEY")

  balance = client.balance_of("0xYourWalletAddress")

  if balance > 0:
      print("Wallet has an active SBT and credit history.")
  else:
      print("No SBT found. This wallet has not yet taken a loan.")
  ```

  ```bash REST theme={null}
  curl -X GET "https://api.blackswan.finance/v1/credit/0xYourWalletAddress" \
    -H "Authorization: Bearer YOUR_API_KEY"
  ```
</CodeGroup>

For the REST endpoint, a successful `200` response means an SBT exists and includes the wallet's credit data. A `404` response means no SBT has been minted for that wallet.

<Info>
  Because credit identity is based entirely on on-chain history, BlackSwan does not require any identity verification, KYC, or personal data. Your wallet address and its lending behavior are sufficient. This means anyone with an Ethereum wallet can participate and build credit in a fully permissionless way.
</Info>