Circle Agent Stack

Circle Agent Stack Starter Kits are six open-source terminal applications that give an agent a wallet and USDC so it can pay for x402 and nanopayment-enabled services autonomously. Each kit wires Circle agent wallets, nanopayments, and the Circle Agent Marketplace into a different agent framework and drops you into an interactive chat with the agent.

Rather than defining a typed tool per Circle command, every kit gives its agent a shell, a file reader, and a grep, and lets the agent run the circle CLI in the shell next to curl, jq, and npm. A command Circle releases later works without a change to the kits. Instructions are not shipped either: on first run the agent fetches Circle's setup file and installs the skills into ~/.agents/skills, the tool-neutral store other agent skill directories symlink into, and the system prompt carries only their names, descriptions, and paths.

Approval is attached to the command rather than the tool. Before any command that moves USDC — services pay, wallet transfer, bridge transfer, gateway deposit, wallet sign, or a spending-cap change — the exact command is printed and waits for confirmation; everything else runs unprompted, so the kits are not a sandbox. The harder limit is set on the wallet itself with per-transaction, daily, weekly, and monthly caps via circle wallet limit set, which confirms by one-time code and holds regardless of what the agent is persuaded to do.

Three workspace packages hold what the kits share: kit-core (tool bodies, shell, approval gate, skill discovery, instructions, slash-command router, pinned balance readout, theme), circle-tools (CLI wrappers for the terminal chrome), and agent-cli (an Ink-based chat interface and a retry and timeout wrapper). Each kit is then a config, an agent wiring file, a thin tools file, a theme, and a chat loop. The samples are for Arc testnet use and are described as not production-ready.

Features

• Six framework kits: LangChain Deep Agents, Claude Agent SDK, Mastra, OpenAI Agents SDK, Vercel AI SDK, and Google Agent Development Kit, differing only where the framework's approval hook and built-in tools differ
• Shell-first tool surface: a shell, a file reader, and a grep instead of a typed tool per Circle command, so new CLI commands work without a release
• Skills off disk: the agent installs Circle's published skills into ~/.agents/skills on first run, shared with other agents on the machine
• Per-command approval: money-moving commands print the exact command and wait for confirmation; the list lives in one editable file
• Wallet spending caps: per-transaction, daily, weekly, and monthly limits set on the wallet itself and confirmed by one-time code
• Terminal chat interface: a scrolling log with a pinned input showing the live USDC balance, plus /help, /wallets, /balance, /gateway, and /discover commands answered from the CLI without a model turn
• Marketplace flow: find or select a service on the Circle Agent Marketplace and pay for it once the command is approved
• Shared packages: kit-core, circle-tools, and agent-cli keep the per-kit code to a config, an agent file, tools, a theme, and a loop