> ## 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 Nanopayments
> Gas-free USDC nanopayments down to $0.000001, powered by Circle Gateway batched settlement
[Circle Gateway](/gateway) enables gas-free USDC nanopayments by batching
thousands of payments into a single onchain transaction. Instead of settling
each payment individually, buyers sign offchain authorizations and Gateway
settles net positions in bulk, eliminating per-transaction gas costs and making
sub-cent payments economically viable. Gateway Nanopayments power agentic
commerce by giving developers and AI agents a financial rail purpose-built for
high-frequency agentic payments at scale.
Gateway Nanopayments and x402 batch settlement require EOA signatures and do not
support ERC-1271. For standard Gateway transfers with smart contracts or smart
contract wallets, see
[ERC-1271 programmable authorization](/gateway/references/erc-1271).
## Key features
Buyers sign payment authorizations offchain at zero gas cost. Gateway
settles in bulk, so neither party pays per-transaction fees.
Send as little as \$0.000001 USDC per payment. Batched settlement keeps fees
from exceeding the payment itself.
Sellers receive payments in their Gateway balance and can withdraw to any
supported blockchain.
## What you can build
Enable AI agents to pay autonomously for compute, data, memory, and services.
Agents transact at high frequency and extreme granularity, executing thousands
of sub-cent payments per minute without gas friction. For the agent-builder
workflow, see [Agent nanopayments](/agent-stack/agent-nanopayments).
Charge per API call, per second of compute, or per dataset access. With
transaction costs near zero, fine-grained billing models become practical for
the first time.
Build decentralized marketplaces where services, models, and data is priced and
traded in real time at sub-cent granularity.
Implement pay-per-second content, micro-rewards, and continuous value flows
where traditional payment rails are too expensive to operate.
## How it works
Gateway Nanopayments enables the [x402 protocol](/x402-facilitators/x402), an
open standard built on the HTTP `402 Payment Required` status code, by using
Circle Gateway's
[batched settlement](/gateway-nanopayments/concepts/batched-settlement)
infrastructure. Instead of settling each x402 payment individually onchain,
Gateway aggregates signed payment authorizations and settles net positions in
bulk. This is what makes sub-cent x402 payments economically viable.
The end-to-end flow is:
1. A buyer deposits USDC into a Gateway Wallet contract (one-time onchain
transaction).
2. A buyer requests a paid resource from a seller's API.
3. The seller responds with `402 Payment Required` and payment details.
4. The buyer signs an EIP-3009 payment authorization (offchain, zero gas).
5. The buyer retries the request with the signed authorization attached.
6. The seller verifies the signature and serves the resource immediately.
7. Gateway collects authorizations and settles them in batches onchain,
crediting the seller's Gateway balance.
## Get started
Deposit USDC, pay for an x402-protected resource without gas fees, and check
your balance
Add payment middleware to your Express API and start accepting gasless USDC
payments
Learn about the open payment protocol that powers Gateway Nanopayments
Understand how Gateway aggregates payments and settles them onchain
Explore the API endpoints for Gateway Nanopayments