> ## 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.

# Gateway webhook events

> Reference for Gateway webhook event types, payload schemas, and example notifications.

Gateway sends webhooks for events on registered wallet addresses. All webhooks
use the V2 notification format. The `notificationType` field names the event,
and the `notification` field contains event data.

```json theme={null}
{
  "subscriptionId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "notificationId": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
  "notificationType": "gateway.deposit.finalized",
  "notification": {
    "...": "Event-specific data. Schema varies by notificationType."
  },
  "timestamp": "2026-04-22T12:00:00.000000000Z",
  "version": 2
}
```

## Deposit events

### `gateway.deposit.finalized`

Fires after tokens are deposited into a Gateway Wallet, the onchain transaction
is finalized, and Gateway processes the deposit.

### Payload fields

| Field | Type | Description |
| - | - | - |
| `id` | string | Unique notification identifier |
| `walletAddress` | string | Registered wallet address that owns the funds. |
| `domain` | string | Chain domain identifier (for example, `"0"` for Ethereum) |
| `env` | string | Network environment: `"testnet"` or `"mainnet"` |
| `tokenAddress` | string | Token contract address |
| `amount` | string | Transfer amount in decimal format (for example, `"1.000000"` for 1 token) |
| `from` | string | Address that initiated the onchain deposit. May be the wallet owner or a delegate acting on their behalf. |
| `to` | string | Destination address |
| `txHash` | string | Onchain transaction hash |

### Example: `gateway.deposit.finalized`

```json theme={null}
{
  "subscriptionId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "notificationId": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
  "notificationType": "gateway.deposit.finalized",
  "notification": {
    "id": "c3d4e5f6-a7b8-9012-cdef-123456789012",
    "walletAddress": "0xf70da97812cb96acdf810712aa562db8dfa3dbef",
    "domain": "0",
    "env": "mainnet",
    "tokenAddress": "0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
    "amount": "1000.000000",
    "from": "0xf70da97812cb96acdf810712aa562db8dfa3dbef",
    "to": "0x19330d10d9cc8751218eaf51e8885d058642e08a",
    "txHash": "0x9a8b7c6d5e4f3a2b1c0d9e8f7a6b5c4d3e2f1a0b9c8d7e6f5a4b3c2d1e0f9a8b"
  },
  "timestamp": "2026-04-22T12:05:00.000000000Z",
  "version": 2
}
```

## Mint events

The `gateway.mint.finalized` and `gateway.mint.forwarded` events share a payload
schema. Mint event payloads include an `attestations` array. Each burn intent in
a transfer maps to one attestation entry. A single transfer can include multiple
burn intents, each with its own recipient and amount.

### `gateway.mint.finalized`

Fires when an attestation is used and tokens are minted on the destination
blockchain. The `wasForwarded` field shows whether the transfer used the
[forwarding service](/gateway/references/forwarding-service).

### `gateway.mint.forwarded`

Fires when a forwarded mint relay is confirmed. This event only occurs for
transfers that use the
[forwarding service](/gateway/references/forwarding-service).

### Payload fields

| Field | Type | Description |
| - | - | - |
| `transferId` | string | Transfer identifier (attestation group ID) |
| `txHash` | string | Onchain transaction hash on the destination blockchain |
| `walletAddress` | string | The depositor that owns the funds on the source chain |
| `domain` | string | Blockchain domain identifier for the destination blockchain (for example, `"7"` for Base) |
| `env` | string | Network environment: `"testnet"` or `"mainnet"` |
| `tokenAddress` | string | Token contract address on the destination blockchain |
| `wasForwarded` | boolean | Whether the transfer used the forwarding service (`gateway.mint.finalized` only) |
| `attestations` | array | Array of attestation details (see below) |

**Attestation fields**

| Field | Type | Description |
| - | - | - |
| `from` | string | The depositor address that triggered the burn on the source blockchain |
| `to` | string | Recipient address for this attestation |
| `amount` | string | Amount in decimal format (for example, `"1.000000"` for 1 token) |
| `transferSpecHash` | string | Transfer specification hash for this attestation |

### Example: `gateway.mint.finalized`

```json theme={null}
{
  "subscriptionId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "notificationId": "f6a7b890-1234-5678-cdef-901234567890",
  "notificationType": "gateway.mint.finalized",
  "notification": {
    "transferId": "a7b89012-3456-7890-abcd-ef1234567890",
    "txHash": "0x1ea922932e2bbefab697b931aa423a6ebe4a683947a5bd105bb38958e52017a5",
    "walletAddress": "0xf70da97812cb96acdf810712aa562db8dfa3dbef",
    "domain": "7",
    "env": "mainnet",
    "tokenAddress": "0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
    "wasForwarded": false,
    "attestations": [
      {
        "from": "0xf70da97812cb96acdf810712aa562db8dfa3dbef",
        "to": "0x7777777700000000000000000000000000000001",
        "amount": "93516.491888",
        "transferSpecHash": "0x4a5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b"
      }
    ]
  },
  "timestamp": "2026-04-22T12:10:00.000000000Z",
  "version": 2
}
```

### Example: `gateway.mint.forwarded`

This event fires only for transfers that use the forwarding service.

```json theme={null}
{
  "subscriptionId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "notificationId": "0a1b2c3d-4e5f-6789-abcd-ef0123456789",
  "notificationType": "gateway.mint.forwarded",
  "notification": {
    "transferId": "b8c90123-4567-8901-abcd-ef2345678901",
    "txHash": "0x2bc033043d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a",
    "walletAddress": "0xf70da97812cb96acdf810712aa562db8dfa3dbef",
    "domain": "3",
    "env": "mainnet",
    "tokenAddress": "0xcccccccccccccccccccccccccccccccccccccccc",
    "attestations": [
      {
        "from": "0xf70da97812cb96acdf810712aa562db8dfa3dbef",
        "to": "0x8888888800000000000000000000000000000002",
        "amount": "50000.000000",
        "transferSpecHash": "0x5b6c7d8e9f0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c"
      }
    ]
  },
  "timestamp": "2026-04-22T12:15:00.000000000Z",
  "version": 2
}
```