> ## Documentation Index > Fetch the complete documentation index at: https://docs.brickken.com/llms.txt > Use this file to discover all available pages before exploring further. # approve > Prepares unsigned transactions for the approve method. Prepares unsigned transactions for approving a spender to use tokens on behalf of the signer. This endpoint is equivalent to calling `/prepare-transactions` with `method=approve`. ## OpenAPI ````yaml POST /prepare-transactions/approve openapi: 3.1.0 info: title: Brickken API V2 description: >- Welcome to the Brickken API documentation. This API allows customers to create and manage tokenization processes, including creating new tokenizations, minting/burning/transferring tokens, whitelisting users, manage tokens approvals. This documentation provides detailed information on how to use the API, including the necessary endpoints, request formats, and expected responses.
**Authentication**All API requests require an API key for authentication. Include your API key in the `x-api-key` header of each request:
```
      x-api-key: YOUR_API_KEY
    ```
Ensure that your API key is kept secure and not shared publicly. A common parameter for all requests is the `signerAddress`. Such address MUST be whitelisted in our factory. To whitelist an address and/or request an API key either for sandbox/production environment please contact with: support@brickken.com. Once a `signerAddress` performs a `newTokenization` we refer to that address as the tokenizer. The tokenizer will be the only one allowed to mint such token, distribute dividends on such token and whitelist/blacklist investors of such token. Regarding actions like transferring tokens or burning tokens, the `signerAddress` can be any user and not only the tokenizer.
**Supported Networks & Addresses**
Sepolia (sandbox environment only)
```
      Chain Id: "aa36a7"
      Factory Address: "0x933ABAA95a7Fd0Bc683bDe2adB89f4C5EA64897b"
      BKN Address: "0x97a13487f889dc770Ac925Be2d3b6c833FA7746a"
      USDT Address: "0x28d2B01854D0aBec267a3DDcad9163580E6E8604"
      USDC Address: "0xb10cE8e28aEb1ae27b968Fb3bfed2FD7dd52daCb"
    ```
Base Sepolia (sandbox / testing)
```
      Chain Id: "84532" (hex "14a34")
      x402 USDC (Circle, EIP-3009): "0x036CbD53842c5426634e7929541eC2318f3dCF7e"
      ERC-8004 Identity Registry: "0x8004A818BFB912233c491871b3d84c89A494BD9e"
      ERC-8004 Reputation Registry: "0x8004B663056A597Dffe9eCcC1965A193B7388713"
    ```
Ethereum mainnet (production environment only)
```
      Chain Id: "1"
      Factory Address: "0x91af681C85Ca98Efc5D69C1B62E6F435030969Db"
      BKN Address: "0x0A638F07ACc6969abF392bB009f216D22aDEa36d"
      USDT Address: "0xdac17f958d2ee523a2206206994597c13d831ec7"
      USDC Address: "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48"
    ```
Base mainnet (production environment only)
```
      Chain Id: "2105"
      Factory Address: "0x278D7bdc2451B0Fa4087A68ce084a86cB91D4d83"
      BKN Address: "0xddB293BB5C5258F7484A94a0fBd5c8B2F6E4e376"
      USDT Address: N/A
      USDC Address: "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913"
    ```
BNB Smart Chain mainnet (production environment only)
```
      Chain Id: "38"
      Factory Address: "0xCe4529Fe88df480BD777d3e32dfD7032e6C685ff"
      BKN Address: "0x0e28bC9B03971E95acF9ae1326E51ecF9C55B498"
      USDT Address: "0x55d398326f99059fF775485246999027B3197955"
      USDC Address: "0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d"
    ```
Avalance C Chain mainnet (production environment only)
```
      Chain Id: "a86a"
      Factory Address: "0xc6c230FA8F40022dE997727436Fae01caAbcDe61"
      BKN Address: "0xd44E4Dc8bdF7C1c62CfDBb182022097BA42Ac6bC"
      USDT Address: "0x9702230A8Ea53601f5cD2dc00fDBc13d4dF4A8c7"
      USDC Address: "0xB97EF9Ef8734C71904D8002F8b6Bc66Dd9c48a6E"
    ```
**Usage Workflow**
1. **Prepare Transactions:**- Use the `POST /prepare-transactions` endpoint with the desired method (e.g., `newTokenization`, `mintToken`, etc...) to prepare the transaction(s). - The response will include an array of unsigned transactions that needs to be signed.
**Example Of An Endpoint Response:**```json { "transactions": [ { "from": "0xSignerAddress", "to": "0xTargetAddress", "value": { "type": "BigNumber", "hex": "0x00" }, "nonce": 1, "chainId": 11155111, "data": "0x...", "type": 2, "maxPriorityFeePerGas": { "type": "BigNumber", "hex": "0x..." }, "maxFeePerGas": { "type": "BigNumber", "hex": "0x..." }, "gasLimit": { "type": "BigNumber", "hex": "0x..." } } ] } ```
2. **Sign the Transactions:**- Use your preferred method or wallet to sign the transaction data provided in the response. - Ensure that the signer address matches the `signerAddress` provided in the initial request.
**Example Of signing a transaction with typescript and `ethers-js`:**```typescript const tx = {...} // One of the object in the array returned by the `/prepare-transactions` endpoint const privateKey = process.env.PRIVATE_KEY; const wallet = new ethers.Wallet(privateKey); const signedTx = await wallet.signTransaction(tx); console.log('Signed Transaction:', signedTx); ```
**NOTE:** Be sure to have enough funds in the signer wallet to cover for the transaction cost
3. **Submit Signed Transactions:**- Use the `POST /send-transactions` endpoint to submit the signed transaction(s) along with the required parameters. - The API will process the transactions, send them to the blockchain, and update the Brickken database accordingly.
4. **Check Transaction Status:**- Use the `GET /get-transaction-status` endpoint to check the status of your transaction. - Provide either the on-chain transaction hash (`hash`) or the internal transaction ID (`txId`) to retrieve the status.
**Environments**The API is available in several environments for testing and production purposes:- Sandbox: `https://api.sandbox.brickken.com/` - Master (Production): `https://api.brickken.com/`
The API also exposes x402scan discovery facade endpoints under /x402/... The public discovery target is https://api.brickken.com, with /.well-known/x402 returning resource URLs and /openapi.json returning the generated OpenAPI 3.1 document. version: 2.0.0 servers: - url: https://api.sandbox.brickken.com description: Sandbox Environment - url: https://api.brickken.com description: Production Environment security: - apiKeyAuth: [] paths: /prepare-transactions/approve: post: tags: - Endpoints - Prepare Transactions summary: approve description: Prepares unsigned transactions for the approve method. requestBody: required: true content: application/json: schema: type: object description: Request body for approve. required: - method - signerAddress - chainId - tokenSymbol - spenderAddress - amount properties: method: type: string enum: - approve description: Required. Must be `approve`. signerAddress: type: string description: >- Required. Wallet address that will sign the prepared transaction. chainId: type: string description: >- Required. Blockchain network identifier. Hex format is recommended, for example Sepolia `aa36a7`. tokenSymbol: type: string description: >- Required. Token symbol to approve. Can be a tokenized asset symbol or a payment token symbol such as BKN, USDT, USDC, USDt, or HAI. spenderAddress: type: string description: Required. Address being approved to spend tokens. pattern: ^0x[a-fA-F0-9]{40}$ amount: type: string description: Required. Allowance amount to approve. investorAddress: type: string description: >- Optional. Token owner address for payment-token approvals. Defaults to signerAddress. pattern: ^0x[a-fA-F0-9]{40}$ tokenizerAddress: type: string description: >- Optional. Conditionally required when approving payment tokens (BKN, USDT, USDC, USDt, or HAI) so the API can resolve the tokenizer scope. pattern: ^0x[a-fA-F0-9]{40}$ tokenizerEmail: type: string description: >- Optional. Tokenizer email override for payment-token approvals. format: email investmentId: type: string description: >- Optional. Investment identifier to associate with this approval. gasLimit: type: string description: >- Optional. Gas limit override. If omitted, the API estimates gas automatically. privateRpcUrl: type: string description: >- Optional. Private RPC URL override. If omitted, the API uses the configured RPC for chainId. nonce: type: integer description: >- Optional. Nonce override. If omitted, the API reads the pending nonce from the RPC. example: method: approve signerAddress: '0x742d35Cc6634C0532925a3b8D4C9db96c4b4d8b' chainId: aa36a7 tokenSymbol: USDT spenderAddress: '0x3333333333333333333333333333333333333333' amount: '100' tokenizerAddress: '0x4444444444444444444444444444444444444444' example: method: approve signerAddress: '0x742d35Cc6634C0532925a3b8D4C9db96c4b4d8b' chainId: aa36a7 tokenSymbol: USDT spenderAddress: '0x3333333333333333333333333333333333333333' amount: '100' tokenizerAddress: '0x4444444444444444444444444444444444444444' responses: '200': description: Successful response content: application/json: schema: type: object properties: transactions: type: array items: type: object txId: type: string required: - transactions - txId security: - apiKeyAuth: [] components: securitySchemes: apiKeyAuth: type: apiKey in: header name: x-api-key ````