Circle is accelerating its push into AI-driven payments as autonomous agents increasingly initiate transactions, according to a Shoal Research report examining the company's Agent Stack ecosystem.

The report analyzes Circle's Agent Stack — comprising wallets, Nanopayments, service discovery, and developer tools — and details how AI agents can hold funds, follow spending rules, discover services, and execute payments programmatically without manual approval. The emergence of agent-driven commerce represents a shift from human-initiated card and bank payments toward software-triggered transactions on blockchain rails, where settlement costs and programmability advantages become decisive.

USDC Gains Ground in Agent Payment Activity

Software can trigger large volumes of agent payments autonomously, meaning transaction counts and payment volumes may serve as better indicators of agent activity than traditional metrics.

While USDT commands roughly $185 billion in circulation compared with $73 billion for USDC, the latter has captured the majority of combined USDC and USDT transfer volume. USDC's monthly transaction count has increased approximately fivefold over the past two years.

The report highlights x402, a protocol enabling agents to pay for web resources through HTTP requests. USDC served as the initial payment rail and continues to settle about 99% of x402 transaction volume — a figure corroborated by Artemis data cited by Shoal Research. This positions Circle favorably as AI agents adopt programmable payment systems. Traditional payment rails like card networks carry per-transaction fees and minimum charge thresholds that make high-frequency, low-value agent payments impractical; stablecoin transfers on blockchains bypass those constraints.

Circle Adds Tools for Autonomous Payments

In May 2026, Circle launched the Circle Agent Stack with five core components: Nanopayments, Agent Wallets, the Circle CLI, Agent Marketplace, and Circle Skills.

Nanopayments support transfers as small as $0.000001, using Circle Gateway to batch authorizations and reduce settlement costs. Agent Wallets allow agents to manage funds under preset spending policies, with operators able to configure spending limits, allowlists, blocklists, and permitted transaction types.

The Circle CLI provides developers with an interface for wallets, CCTP — Circle's Cross-Chain Transfer Protocol that moves USDC natively across supported blockchains without bridge wrappers — Gateway, and policy management. Agent Marketplace helps agents discover x402-compatible services, while Circle Skills supplies information for AI coding tools.

Competition Across Payment Rails

Circle's Agent Stack is built on USDC, but several companies are developing competing autonomous payment systems. Coinbase created x402 and operates its default facilitator, alongside offering AgentKit, CDP wallets, and the Base network.

Stripe has developed Tempo and the Machine Payments Protocol, supporting stablecoins, cards, and Bitcoin. Tether has pursued AI payments through its QVAC SDK and Wallet Development Kit. The breadth of entrants underscores that agent payments are emerging as a contested infrastructure layer, with outcomes likely shaped by which rails developers integrate by default.

The Shoal Research report also flags a potential challenge for Circle's business model: agents may drive higher transaction activity by using funded wallets more frequently, increasing velocity without proportional growth in stablecoin balances.

Circle has scheduled Arc's mainnet launch for September 2026, with USDC designated as its native gas token.