Circle Agent Stack Starter Kits

Open-source starter kits for developers building agent harnesses that need access to wallets and USDC to autonomously pay for x402 and Nanopayment-enabled services via the Circle Agent Stack. Each kit wires the Agent Stack — agent wallets, nanopayments, and the Circle Agent Marketplace — into a different popular AI agent framework and drops you into an interactive terminal chat with the agent.

Kits

Kit	Framework	Docs
kits/langchain	LangChain Deep Agents	https://docs.langchain.com/oss/javascript/deepagents/overview
kits/claude-agent-sdk	Claude Agent SDK	https://code.claude.com/docs/en/agent-sdk/overview
kits/mastra	Mastra	https://mastra.ai/docs
kits/openai-agents	OpenAI Agents SDK	https://openai.github.io/openai-agents-js
kits/vercel-ai	Vercel AI SDK	https://sdk.vercel.ai/docs
kits/google-adk	Google Agent Development Kit	https://adk.dev/get-started/typescript/

Shared packages

Everything a kit does not have to write for itself lives in one of three workspace packages, so the kits differ only where their frameworks genuinely differ:

• packages/circle-tools: framework-agnostic wrappers around the Circle CLI (wallets, balances, service discovery, x402 payments).
• packages/kit-core: the shared kit layer — marketplace skill fetching and the bootstrap prompt, the single-sourced tool and parameter descriptions, the payment preflight/approval helpers, and the terminal theme.
• packages/agent-cli: reusable Ink-based terminal chat UI (scrolling log + pinned bottom input) and the retry/timeout wrapper shared by the kits.

Repository layout

agent-stack-starter-kits/
├── kits/
│   ├── claude-agent-sdk/
│   ├── google-adk/
│   ├── langchain/
│   ├── mastra/
│   ├── openai-agents/
│   └── vercel-ai/
└── packages/
    ├── circle-tools/         # Circle CLI wrappers
    ├── kit-core/             # shared skill / tool copy / preflight / theme
    └── agent-cli/            # shared terminal chat UI + retry

Each kit is deliberately thin: a config.ts, an agent.ts wiring its framework's agent and approval hook, a tools.ts adapting the shared descriptions and preflight helpers to that framework's tool API, a theme.ts that only names the kit's log tag, and an index.ts driving the chat loop.

Prerequisites

• Node.js 20+
• Bun 1.2+ (workspace manager)
• Circle CLI: bun add -g @circle-fin/cli
• Circle Agent Skills (one of):
  • circle skill install --tool <claude-code|cursor|codex|opencode|amp>
  • Universal fallback: bunx skills add circlefin/skills -g
• A Circle account and API key

Install

bun install

This installs all workspace dependencies from the repo root. Each kit owns its own .env.example (copy to .env inside that kit's folder) and exposes a bun run demo entrypoint. See its README for details.

Demo use case

Each kit's bun run demo launches an interactive terminal chat (a shared Ink-based UI with a scrolling log and a pinned input showing your live USDC balance) that demonstrates the same flow:

1. Bootstrap with the Circle Agent Skill + CLI
   • Install CLI and skill
   • Login
   • Create a wallet
   • Check / fund balance
2. Transact via the agent
   • Find or select a service on the Circle Agent Marketplace
   • Pay for it via the agent

See each kit's README.md for run instructions.

Key resources

• Circle Agent Stack docs
• Circle Skills setup
• Circle CLI reference
• Agent Wallets quickstart
• Agent Nanopayments quickstart
• Circle Agent Marketplace
• Circle Developer Discord

Legal disclaimer

Sample apps provided for demonstration and educational purposes only, intended for Arc testnet use only, and not production-ready. See Arc.io for more.