steward-sdk

If your agent pays anyone in USDC on Arc, put STEWARD in front of it: one contract call gives you per-payee caps + period limits + expiry the agent can't exceed, an on-chain decision log, and an escalation path. Ten lines.

Contracts + docs: https://github.com/big14way/steward (Tameion Agents Hackathon, Canteen × Circle × Arc).

TypeScript

npm i steward-arc-sdk viem

import { Steward } from "steward-arc-sdk";
import { privateKeyToAccount } from "viem/accounts";

const s = new Steward({
  allowanceManager: "0x…",   // the owner created an allowance for your agent address + the payee
  auditLog: "0x…",
  account: privateKeyToAccount(process.env.AGENT_PK as `0x${string}`),
});

// rules → canonical hash → AuditLog.record() → pay() | escalate()
const r = await s.decide({
  allowanceId: 0n, amount: 150_000_000n, memo: "logo v2",
  inputs: { milestone: "logo v2", evidence: "ipfs://…" }, evidence: true, screenOk: true,
  reason: "Milestone delivered with evidence; within per-tx and period caps.",   // your LLM's text, never an amount
});
console.log(r.action, r.hash, r.payTx ?? r.escalateTx);

What decide does: SCREEN_FAIL if screenOk === false · HOLD if evidence === false · ESCALATE if over the per-tx cap or no room · PARTIAL if only part fits (pays that part, escalates the rest under keccak256("STEWARD/remainder" ‖ hash)) · else PAY. Every outcome is record()ed on AuditLog with the keccak256 of a canonical JSON record you get back (r.canonical), so an auditor can replay it. A decision hash pays once, even if you retry. Arc's 20 gwei floor is handled.

Python

pip install steward-sdk

from steward_sdk import Steward

s = Steward(allowance_manager="0x…", audit_log="0x…", agent_private_key=os.environ["AGENT_PK"])
r = s.decide(allowance_id=0, amount=150_000_000, memo="logo v2",
             inputs={"milestone": "logo v2", "evidence": "ipfs://…"}, evidence=True, screen_ok=True)
print(r.action, r.hash, r.pay_tx or r.escalate_tx)

Agent on a Circle wallet (no raw key)

Most Arc agents sign with a Circle Developer-Controlled wallet. Pass the Circle client you already have instead of account; STEWARD sends record, pay and escalate through Circle's contract-execution API and waits for the on-chain hash. The allowance's agent must be that wallet's address. Same rules, same hashes.

import { initiateDeveloperControlledWalletsClient } from "@circle-fin/developer-controlled-wallets";
import { Steward } from "steward-arc-sdk";

const client = initiateDeveloperControlledWalletsClient({ apiKey: process.env.CIRCLE_API_KEY!, entitySecret: process.env.CIRCLE_ENTITY_SECRET! });
const s = new Steward({
  allowanceManager: "0x3AAfC635a1D1391c9FD8b5B9d8A518Fe980cb7E6",   // Arc Testnet
  auditLog: "0x89264D27AFbCb2Ac90b8a3802340C26Ea1326866",
  circle: { client, walletId: process.env.AGENT_WALLET_ID! },
});
const r = await s.decide({ allowanceId: 0n, amount: 150_000_000n, memo: "logo v2", inputs: { milestone: "logo v2" } });

# pip install "steward-sdk[circle]"
from circle.web3 import utils
from steward_sdk import Steward

client = utils.init_developer_controlled_wallets_client(api_key=os.environ["CIRCLE_API_KEY"], entity_secret=os.environ["CIRCLE_ENTITY_SECRET"])
s = Steward(allowance_manager="0x3AAfC635a1D1391c9FD8b5B9d8A518Fe980cb7E6", audit_log="0x89264D27AFbCb2Ac90b8a3802340C26Ea1326866",
            circle_client=client, circle_wallet_id=os.environ["AGENT_WALLET_ID"])
r = s.decide(allowance_id=0, amount=150_000_000, memo="logo v2", inputs={"milestone": "logo v2"})

Tested live on Arc Testnet with both SDKs (a HOLD recorded through a Circle wallet: TypeScript, Python).

Owner side

The owner (a Circle Developer-Controlled wallet in the reference app) calls create(agent, payee, capPerPeriod, perTxCap, period, expiry), fund(id, amount), approveAndPay(id, amount, hash) for escalations, and revoke(id) to pull unspent funds and lock the agent out. The reference FastAPI service + Telegram bot in the main repo does this with one tap.