Circle Agent Stack for AI agents: USDC wallets, spend policies, transfers, and x402 nanopayments.
MCP server for Circle's Agent Stack. Create wallets, set spend policies, send USDC, and pay x402-priced endpoints — all from a tool call.
npx circle-agent-stack-mcp
| Tool | What it does |
|---|---|
circle_wallet_create | Create an agent wallet (dev/hosted/smart) |
circle_wallet_list | List wallets with USDC balances |
circle_balance | Balance + last 10 txns for a wallet |
circle_policy_set | Set daily cap, x402 cap, allow/block lists |
circle_transfer_usdc | Send USDC to an on-chain address |
circle_x402_pay | Pay an x402-priced endpoint and return its response |
You need the Circle CLI installed and authenticated:
npm install -g @circle-fin/circle-cli
circle login
export CIRCLE_API_KEY=your_key_here
{
"mcpServers": {
"circle": {
"command": "npx",
"args": ["-y", "circle-agent-stack-mcp"],
"env": {
"CIRCLE_API_KEY": "your_key_here"
}
}
}
}
claude mcp add circle -- npx -y circle-agent-stack-mcp
You: Create a dev wallet called eva-treasury, set a $5 daily cap and $0.10 x402 cap,
then fetch today's BTC signal from the x402 endpoint at https://signals.example.co/btc
Claude:
→ circle_wallet_create("eva-treasury", type="dev")
{ wallet_id: "wal_abc123", address: "0x..." }
→ circle_policy_set("wal_abc123", daily_cap_usdc=5, x402_cap_usdc=0.10)
{ status: "applied" }
→ circle_x402_pay("wal_abc123", "https://signals.example.co/btc", max_price_usdc=0.10)
{ signal: "LONG", confidence: 0.72, price_paid_usdc: 0.05 }
Today's BTC signal: LONG (72% confidence). Paid $0.05.
http-server.ts wraps the same tools behind an x402 paywall — agents pay per call in USDC rather than using an API key. Useful if you want to expose Circle tooling as a paid service.
CIRCLE_PAYOUT_ADDRESS=0x... npm run start:http
To test the x402 flow locally, run the toy demo server in examples/x402-demo-server.mjs.
v0.1 shells out to the Circle CLI for all operations. This keeps auth handling out of this repo and avoids reimplementing the API client before the tool surface is validated. v0.2 will switch to direct HTTP via @circle-fin/circle-sdk.
Your Circle API key has spend authority. Always:
daily_cap_usdc before enabling automated paymentstype="dev" wallets, not mainnetallowlist before moving to productionCIRCLE_API_KEYcircle_nanopayment_stream — streaming x402 payments for per-token billingcircle_skills_list / circle_skills_call — Circle Skills marketplaceSource-derived launch command. Check the maintainer’s required arguments and credentials before running:
npx -y circle-agent-stack-mcpMerge this template into ~/Library/Application Support/Claude/claude_desktop_config.json. Keep existing servers. Add any arguments, credentials, and permissions required by the maintainer; this template has not been install-tested.
{
"mcpServers": {
"io-github-kinance-circle-agent-stack-mcp": {
"command": "npx",
"args": [
"-y",
"circle-agent-stack-mcp"
]
}
}
}Restart Claude Desktop completely for changes to take effect. Confirm the server appears connected in the client’s tool list, then try a read-only example from its documentation.
Claude Desktop setup referencecircle-agent-stack-mcpnpmio.github.kinance/circle-agent-stack-mcp works with any MCP-compatible client. Copy the config snippet from the Configuration section above and add it to the file shown for your client, then restart the application.
~/Library/Application Support/Claude/claude_desktop_config.jsonRestart Claude Desktop completely for changes to take effect.~/.cursor/mcp.jsonRestart Cursor for changes to take effect..vscode/mcp.jsonReload VS Code window for changes to take effect.~/.codeium/windsurf/mcp_config.jsonRestart Windsurf for changes to take effect..mcp.jsonSave at the project root, then start Claude Code in that project and review the MCP server approval prompt. Keep real credentials out of shared files.