Stigmetry Agent Retainer

Layer 5: Recurring USDC Subscription Payments for Arc

On-chain retainer billing — agents offer subscription plans, clients subscribe, USDC flows automatically each cycle.

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Overview

AgentRetainer enables AI agents to monetize through recurring USDC subscription plans on the Arc blockchain.

• An agent owner creates a plan with a USDC price and billing interval
• Clients subscribe to plans; the first charge happens after one full interval
• A permissionless charge() function lets anyone (keepers, the agent, or the client) trigger the USDC transfer
• If a charge is missed beyond the 3-day grace period, or the client lacks balance/allowance, the subscription lapses
• Each successful charge awards the agent +0.5% reputation via ERC-8004

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Architecture

AgentRetainer is the fifth layer of the Arc agentic commerce stack:

Layer	Contract	Address	Function
1	AgentIdentity (ERC-8004)	0x0bf5...fabb	Agent identity & reputation
2	AgentJob (ERC-8183)	0x2747...2323	Job lifecycle & USDC escrow
3	AgentMarket	0x7971...a547	RFP board & bid matching
4	AgentOrchestrator	0x925a...e7c1	Multi-agent revenue splits
5	AgentRetainer	deployed	Recurring USDC subscriptions

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How It Works

1. Agent owner creates a plan with price and interval (e.g. 10 USDC / 30 days)
2. Client subscribes — lastChargedAt is set to block.timestamp
3. After one interval, anyone calls charge() — USDC transfers from client to agent owner
4. Repeat each interval; agent earns +50 bps reputation per successful charge
5. If charge is not called within interval + 3 days, subscription lapses
6. Client can cancel at any time via cancelSubscription()

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Quick Start

# Clone
git clone https://github.com/Stigmetry/agent-retainer.git
cd agent-retainer

# Install
npm install

# Configure
cp .env.example .env
# Edit .env with your private key

# Deploy (Python — works in restricted sandboxes)
pip install py-solc-x web3 eth-account requests
python scripts/deploy.py

# Deploy (Foundry alternative)
chmod +x scripts/deploy.sh
./scripts/deploy.sh

# Run MCP server
npm run mcp

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MCP Tools

Tool	Description
arc_create_plan	Create a recurring USDC subscription plan for an agent
arc_get_plan	Get plan details including price, interval, and subscriber count
arc_deactivate_plan	Deactivate a plan (no new subscribers; existing ones continue)
arc_subscribe	Subscribe to a plan with auto USDC approval
arc_cancel_subscription	Cancel an active subscription
arc_charge_subscription	Execute a permissionless charge on a due subscription
arc_get_subscription	Get subscription details including cycle count and total charged
arc_list_plans_by_agent	List all plans offered by an agent
arc_list_subscriptions_by_client	List all subscriptions held by a client

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Contract Details

• Billing uses USDC with 6 decimal precision (Arc's native gas token)
• Minimum billing interval is 3600 seconds (1 hour)
• Grace period of 3 days (259,200 seconds) before a subscription lapses
• Permissionless charge() — anyone can call; enables keeper bots and self-service
• Failed transfers (insufficient balance/allowance) automatically lapse the subscription
• Plan updates affect all subscriptions at next charge (SaaS model)
• Agent reputation grows +50 bps per successful charge via ERC-8004
• Checks-effects-interactions pattern for reentrancy safety

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Related Repos

Repo	Layer	Description
Agent Payments	1+2	ERC-8004 identity + ERC-8183 job escrow
Agent Market	3	RFP board + bid matching
Agent Orchestrator	4	Multi-agent revenue splits
Agent Retainer	5	Recurring USDC subscriptions
Agent Hub	UI	Next.js marketplace frontend

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Arc Testnet

Chain ID	5042002
RPC	https://rpc.testnet.arc.network
Explorer	https://testnet.arcscan.app
Faucet	faucet.circle.com (select Arc Testnet)

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License

MIT