> ## 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.

# Webhook events

> Reference for Stablecoin Payins and Stablecoin Payouts webhook event types, payloads, and the notification subscription system.

Stablecoin Payins and Stablecoin Payouts emit webhook events so your server can
react to deposit-address assignment, settled payments, recipient review
outcomes, and payout status changes. Subscribe to these events instead of
polling for status.

* Subscription endpoint: `POST /v1/notifications/subscriptions`
* Setup:
  [Circle APIs notifications quickstart](/circle-mint/references/webhook-notifications)

All payloads use the following envelope structure.

| Envelope field | Type | Description |
| - | - | - |
| `clientId` | string | Your Circle client identifier. |
| `notificationType` | string | Event type identifier. See [Event types](#event-types). |
| `version` | number | Schema version. Always `1`. |
| `<resourceKey>` | object | Event-specific data. The key name varies by event type. |

## Event types

| `notificationType` | Resource key | Trigger |
| - | - | - |
| `paymentIntents` | `paymentIntent` | Intent created, deposit address assigned, or (transient intents) intent completed. |
| `payments` | `payment` | A payin settles, or a refund changes status. Discriminated by `type`. |
| `addressBookRecipients` | `addressBookRecipient` | Recipient status changes, such as `pending` to `active`. |
| `payouts` | `payout` | Payout status changes, such as `pending`, `complete`, or `failed`. |

## Payment intent events

The `paymentIntents` notification fires when you create an intent, when Circle
assigns the deposit address, and—for transient intents—when the intent reaches
`complete`. Continuous intents stay at `active` and never advance to `complete`;
reconcile their transfers through the `payments` event instead.

Status values observed in `timeline[].status`: `created`, `pending`, `active`,
`complete`.

```json Example paymentIntents payload theme={null}
{
  "clientId": "5b057f1e-743c-4aeb-beeb-ef7b2e16f291",
  "notificationType": "paymentIntents",
  "version": 1,
  "paymentIntent": {
    "id": "e2e90ba3-9d1f-490d-9460-24ac6eb55a1b",
    "type": "continuous",
    "currency": "USD",
    "settlementCurrency": "USD",
    "amountPaid": { "amount": "0.00", "currency": "USD" },
    "paymentMethods": [
      {
        "type": "blockchain",
        "chain": "BASE",
        "address": "0x97de855690955e0da79ce5c1b6804847e7070c7f"
      }
    ],
    "timeline": [
      { "status": "pending", "time": "2026-04-12T20:13:38.188286Z" },
      { "status": "created", "time": "2026-04-12T20:13:35.579331Z" }
    ]
  }
}
```

## Payment events

The `payments` notification fires whenever an inbound transfer settles or a
refund changes status. Payments and refunds share this channel and are
discriminated by the `type` field (`payment` or `refund`). The payload links
back to its intent through `paymentIntentId`.

Status values: `pending`, `paid`.

```json Example payments payload theme={null}
{
  "clientId": "5b057f1e-743c-4aeb-beeb-ef7b2e16f291",
  "notificationType": "payments",
  "version": 1,
  "payment": {
    "id": "66c56b6a-fc79-338b-8b94-aacc4f0f18de",
    "type": "payment",
    "status": "paid",
    "amount": { "amount": "1.00", "currency": "USD" },
    "paymentIntentId": "e2e90ba3-9d1f-490d-9460-24ac6eb55a1b",
    "fromAddresses": {
      "chain": "BASE",
      "addresses": ["0x0d4344cff68f72a5b9abded37ca5862941a62050"]
    },
    "depositAddress": {
      "chain": "BASE",
      "address": "0x97de855690955e0da79ce5c1b6804847e7070c7f"
    },
    "transactionHash": "0x7351585460bd657f320b9afa02a52c26d89272d0d10cc29913eb8b28e64fd906"
  }
}
```

## Address book recipient events

The `addressBookRecipients` notification fires when a recipient's status
changes, such as when review completes and the recipient becomes `active`. Wait
for `active` before you send a payout to the recipient.

Status values: `pending`, `inactive`, `active`, `denied`.

```json Example addressBookRecipients payload theme={null}
{
  "clientId": "a03a47ff-b0eb-4070-b3df-dc66752cc802",
  "notificationType": "addressBookRecipients",
  "version": 1,
  "addressBookRecipient": {
    "id": "dff5fcb3-2e52-5c13-8a66-a5be9c7ecbe1",
    "chain": "BASE",
    "address": "0x65bfcf1a6289a0b77b4d3f7d12005a05949fd8c3",
    "status": "active",
    "createDate": "2026-05-01T14:16:34.985353Z",
    "updateDate": "2026-05-01T14:18:02.123456Z"
  }
}
```

## Payout events

The `payouts` notification fires when a payout status changes. The payload
includes the resolved `fees` and onchain `networkFees`.

Status values: `pending`, `complete`, `failed`.

```json Example payouts payload theme={null}
{
  "clientId": "a03a47ff-b0eb-4070-b3df-dc66752cc802",
  "notificationType": "payouts",
  "version": 1,
  "payout": {
    "id": "b8627ae8-732b-4d25-b947-1df8f4007a29",
    "sourceWalletId": "12345",
    "destination": {
      "type": "address_book",
      "id": "dff5fcb3-2e52-5c13-8a66-a5be9c7ecbe1"
    },
    "amount": { "amount": "3000.14", "currency": "USD" },
    "toAmount": { "amount": "3000.14", "currency": "USD" },
    "fees": { "amount": "0.00", "currency": "USD" },
    "networkFees": { "amount": "0.30", "currency": "USD" },
    "status": "complete",
    "createDate": "2026-05-01T14:20:30.000Z",
    "updateDate": "2026-05-01T14:21:12.000Z"
  }
}
```