> ## 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. # How-to: Grant USDC allowance to Permit2 > Grant a USDC token allowance to the Permit2 contract using a Circle Wallets developer-controlled wallet, a headless BYOW wallet, or an EIP-1193 Ethereum wallet For Transactions V2 on EVM blockchains, there is a dependency on the `Permit2` contract to enable allowance management. To get the benefits of Transactions V2, you must grant a USDC token allowance to the `Permit2` contract. This guide shows three examples of how to grant a USDC token allowance to the `Permit2` contract. The [`Permit2` documentation](https://docs.uniswap.org/contracts/permit2/overview) provides additional examples of how to grant this allowance. ## Prerequisites The examples on this page show how to grant a USDC token allowance to the `Permit2` contract using a [Circle Wallets developer-controlled wallet](/wallets/dev-controlled) or a generic EIP-1193 Ethereum wallet. The headless example is for a bring-your-own- wallet (BYOW) OFI that signs transactions in its backend. Before you begin, ensure you have: * If you are following the Circle Wallets example: * A Circle Developer Account * A [developer-controlled wallet](/wallets/dev-controlled/create-your-first-wallet) * **Node.js** and **npm** installed on your development machine * A project set up as described in the following section ### Set up your project 1. Initialize a new Node.js project and install dependencies: ```shell theme={null} npm init -y npm pkg set type=module npm install viem dotenv npm install --save-dev typescript @types/node tsx ``` 2. In the project root, create a `.env` file and add the following variables: ```shell theme={null} USDC_CONTRACT_ADDRESS= PERMIT2_CONTRACT_ADDRESS= APPROVAL_AMOUNT= WALLET_ADDRESS= ``` The `PERMIT2_CONTRACT_ADDRESS` is the same across all EVM blockchains (`0x000000000022D473030F116dDEE9F6B43aC78BA3`), but you should verify it with the blockchain explorer on the chain you are using. You can find the `USDC_CONTRACT_ADDRESS` on the [USDC contract address page](/stablecoins/usdc-contract-addresses). The USDC token has 6 decimals. Set the allowance to cover the expected payment amount plus any associated fees. For a \$100 payment, set `APPROVAL_AMOUNT` to at least `100000000` (100 \* 106) plus the fees converted to raw USDC units. If you are following the Circle Wallets example, you will also need to add the following variables: ```shell theme={null} CIRCLE_WALLET_ID= CIRCLE_WALLETS_API_KEY= ENTITY_SECRET= ``` If you are following the EIP-1193 Ethereum wallet example, or your Circle Wallet is on the generic `EVM` / `EVM-TESTNET` chain, you will also need to add the following variable: ```shell theme={null} RPC_URL= ``` 3. Create an `index.ts` file. You'll add code step by step in the following sections. Run it with `npx tsx index.ts`. ### Grant a USDC token allowance to the `Permit2` contract The following example code shows the process for granting a USDC token allowance to the [`Permit2` contract](https://etherscan.io/address/0x000000000022D473030F116dDEE9F6B43aC78BA3) using a Circle Wallets developer-controlled wallet or an EIP-1193 Ethereum wallet. This example is for a Circle Wallets developer-controlled wallet on specific EVM blockchains (for example, `ETH`, `ETH-SEPOLIA`, `MATIC`, `MATIC-AMOY`, `ARC`, `ARC-TESTNET`, etc.). If your Circle Wallet is on the generic `EVM` / `EVM-TESTNET` chain, use the example in the "Circle Wallets (generic EVM)" tab. ```typescript theme={null} import { initiateDeveloperControlledWalletsClient } from "@circle-fin/developer-controlled-wallets"; import { randomUUID } from "crypto"; import dotenv from "dotenv"; dotenv.config(); export async function approveUSDCWithCircleWallets() { const client = initiateDeveloperControlledWalletsClient({ apiKey: process.env.CIRCLE_WALLETS_API_KEY!, entitySecret: process.env.ENTITY_SECRET!, }); const response = await client.createContractExecutionTransaction({ walletId: process.env.CIRCLE_WALLET_ID!, contractAddress: process.env.USDC_CONTRACT_ADDRESS!, abiFunctionSignature: "approve(address,uint256)", abiParameters: [ process.env.PERMIT2_CONTRACT_ADDRESS!, process.env.APPROVAL_AMOUNT!, ], idempotencyKey: randomUUID(), fee: { type: "level", config: { feeLevel: "MEDIUM" } }, }); return response.data; } /* -------- Example usage with Circle --------- // For auth and wallet creation, see: https://developers.circle.com/interactive-quickstarts/dev-controlled-wallets const response = await approveUSDCWithCircleWallets(); console.log('Response:', response); ---------------------------------- */ ``` This example is for a Circle Wallets developer-controlled wallet on generic EVM blockchains (for example, `EVM`, `EVM-TESTNET`). You should create chain-specific Circle Wallets (for example, `ETH`, `ETH-SEPOLIA`, `MATIC`, `MATIC-AMOY`, `ARC`, `ARC-TESTNET`) instead of a generic EVM wallet and follow the example in the "Circle Wallets" tab instead. If you're migrating an existing integration, see [How-to: Migrate from transactions V1 to V2](/cpn/guides/transactions/migrate-from-txn-v1-to-v2). ```typescript theme={null} import { initiateDeveloperControlledWalletsClient } from "@circle-fin/developer-controlled-wallets"; import { createPublicClient, http, encodeFunctionData, erc20Abi, type Address, type Hex, } from "viem"; import { sepolia } from "viem/chains"; import dotenv from "dotenv"; dotenv.config(); export async function signTransaction(transaction: Record) { const client = initiateDeveloperControlledWalletsClient({ apiKey: process.env.CIRCLE_WALLETS_API_KEY!, entitySecret: process.env.ENTITY_SECRET!, }); const transactionJson = JSON.stringify( transaction, (_, value) => (typeof value === "bigint" ? value.toString() : value), 2, ); const response = await client.signTransaction({ walletId: process.env.CIRCLE_WALLET_ID!, transaction: transactionJson, }); return response.data; } export async function composeUSDCApprovalTransaction() { const publicClient = createPublicClient({ chain: sepolia, transport: http(process.env.RPC_URL), }); const data = encodeFunctionData({ abi: erc20Abi, functionName: "approve", args: [ process.env.PERMIT2_CONTRACT_ADDRESS as Address, BigInt(process.env.APPROVAL_AMOUNT!), ], }); const fees = await publicClient.estimateFeesPerGas(); const transaction = await publicClient.prepareTransactionRequest({ account: process.env.SENDER_WALLET_ADDRESS as Address, to: process.env.USDC_CONTRACT_ADDRESS as Address, value: 0n, data, ...fees, }); return transaction; } export async function broadcastSignedTransaction(signedTransaction: Hex) { const publicClient = createPublicClient({ chain: sepolia, // use the correct chain for your wallet transport: http(process.env.RPC_URL), }); const txHash = await publicClient.sendRawTransaction({ serializedTransaction: signedTransaction, }); return txHash; } /* -------- Example usage with Circle --------- // For auth and wallet creation, see: https://developers.circle.com/interactive-quickstarts/dev-controlled-wallets const tx = await composeUSDCApprovalTransaction(); const signature = await signTransaction(tx); // Circle's API returns signedTransaction as a hex string const txHash = await broadcastSignedTransaction(signature.signedTransaction as Hex); ---------------------------------- */ ``` This example is for an OFI that holds its own EVM private key and signs from a server or other headless process. Keep the private key in a secret manager and never commit it to your project or expose it to a client. Add these variables to your `.env` file: ```shell theme={null} WALLET_PRIVATE_KEY= RPC_URL= ``` The wallet must hold enough native currency to pay for this one-time ERC-20 approval transaction. The later CPN settlement transaction charges its gas fee in USDC as described in [Create an onchain transaction](/cpn/guides/transactions/create-an-onchain-txn). ```typescript theme={null} import { createPublicClient, createWalletClient, http, erc20Abi, type Address, } from "viem"; import { privateKeyToAccount } from "viem/accounts"; import { sepolia } from "viem/chains"; import dotenv from "dotenv"; dotenv.config(); export async function approveUSDCWithHeadlessWallet() { const account = privateKeyToAccount( process.env.WALLET_PRIVATE_KEY as `0x${string}`, ); const walletClient = createWalletClient({ account, chain: sepolia, transport: http(process.env.RPC_URL), }); const publicClient = createPublicClient({ chain: sepolia, transport: http(process.env.RPC_URL), }); const hash = await walletClient.writeContract({ address: process.env.USDC_CONTRACT_ADDRESS as Address, abi: erc20Abi, functionName: "approve", args: [ process.env.PERMIT2_CONTRACT_ADDRESS as Address, BigInt(process.env.APPROVAL_AMOUNT!), ], }); const receipt = await publicClient.waitForTransactionReceipt({ hash }); return { hash, receipt }; } const result = await approveUSDCWithHeadlessWallet(); console.log("Approval transaction:", result.hash); ``` ```typescript theme={null} import { createWalletClient, createPublicClient, http, custom, erc20Abi, type Address, type EIP1193Provider, } from "viem"; import { sepolia } from "viem/chains"; import dotenv from "dotenv"; dotenv.config(); export async function approveUSDCWithEIP1193Wallet(provider: EIP1193Provider) { const publicClient = createPublicClient({ chain: sepolia, transport: http(process.env.RPC_URL), }); const walletClient = createWalletClient({ account: process.env.WALLET_ADDRESS as Address, chain: sepolia, transport: custom(provider), }); const hash = await walletClient.writeContract({ address: process.env.USDC_CONTRACT_ADDRESS as Address, abi: erc20Abi, functionName: "approve", args: [ process.env.PERMIT2_CONTRACT_ADDRESS as Address, BigInt(process.env.APPROVAL_AMOUNT!), ], }); const receipt = await publicClient.waitForTransactionReceipt({ hash }); return { hash, receipt }; } /* -------- Example usage with EIP-1193 wallet --------- // Refer to https://viem.sh/docs/clients/transports/custom and your wallet provider's documentation for the provider object. const { hash, receipt } = await approveUSDCWithEIP1193Wallet(window.ethereum as EIP1193Provider); console.log('Hash:', hash); console.log('Receipt:', receipt); ---------------------------------- */ ``` For a BYOW OFI, the preceding approval is a one-time ERC-20 transaction. After it confirms, use the same wallet to sign the EIP-712 `messageToBeSigned` returned by the [create transaction V2 endpoint](/api-reference/cpn/cpn-platform/create-transaction-v2). Submit the resulting signature in the `signedTransaction` field of the [submit transaction V2 endpoint](/api-reference/cpn/cpn-platform/submit-transaction-v2).