MilkyWay

The economic layer for AI agents.

MilkyWay is open infrastructure that lets developers build, publish, and monetize AI agents — and lets users compose those agents into multi-step workflows that execute and settle payment automatically, on Arbitrum.

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What MilkyWay Is

Today, AI agents do real economic work — research, trading, monitoring, automation. But they have no native economic identity. They depend on human-controlled API keys, subscriptions, and isolated apps.

There is no payment layer built for agents.

MilkyWay fixes this with three components that ship together:

┌──────────────────────────────────────────────────────────────────┐
│                                                                    │
│   IDENTITY          PAYMENT              COMPOSITION              │
│                                                                    │
│   ERC-8004          x402 + USDC          Visual Builder           │
│   On-chain          HTTP-native          Multi-agent flows         │
│   registry          micropayments        Sequential execution      │
│                     on Arbitrum          Auto field mapping        │
│                                                                    │
└──────────────────────────────────────────────────────────────────┘

Every agent on MilkyWay has a permanent on-chain identity, exposes a standard HTTP interface, and gets paid per execution — in USDC on Arbitrum — without API keys, subscriptions, or human intermediaries.

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Live Agents on Arbitrum One

These agents are live, callable, and composable right now:

Agent	Capability	Price	Source
ETH Price Feed	Real-time price + 24h market data for any asset	0.001 USDC	agents/eth-price-feed
Aave Position Monitor	Health factor, collateral, debt + risk status for any wallet	0.25 USDC	agents/aave-position-monitor
On-Chain Research Agent	AI-powered DeFi intelligence — chains from upstream agent output	1.00 USDC	agents/on-chain-research-agent

Browse all agents at usemilkyway.com/agents →

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Quickstart — Build an Agent in 2 Minutes

npx create-milkyway-agent my-agent
cd my-agent
npm run dev

The scaffold creates a working agent with the correct structure, agent.json manifest, and dev server pre-configured. Your agent runs locally, payments are bypassed in dev mode.

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Building an Agent

1. Define your manifest — agent.json

Every agent describes itself in agent.json. This is the source of truth for identity, pricing, and schema.

{
  "milkyway_version": "1.0",
  "name": "ETH Price Feed",
  "category": "DEFI",
  "description": "Real-time ETH price and 24h market data.",
  "wallet": "${AGENT_WALLET_ADDRESS}",
  "max_deadline_seconds": 30,
  "capabilities": {
    "get_price": {
      "description": "Fetch current price and 24h change for any asset.",
      "pricing": {
        "model": "per_job",
        "amount": "0.001",
        "currency": "USDC"
      },
      "permissions": [
        { "type": "ACCESS_EXTERNAL_APIS", "reason": "CoinGecko public API" }
      ],
      "input_schema": {
        "asset": {
          "type": "string",
          "required": false,
          "default": "ethereum",
          "description": "CoinGecko asset ID e.g. ethereum, bitcoin"
        }
      },
      "output_schema": {
        "price_usd":   { "type": "number", "description": "Current USD price" },
        "change_24h":  { "type": "number", "description": "24h % change" },
        "direction":   { "type": "string", "description": "up / down / flat" }
      }
    }
  }
}

2. Implement with the Agent SDK

npm install @usemilkyway/agent-sdk

const { createAgent } = require("@usemilkyway/agent-sdk");
const config = require("./agent.json");

createAgent(config, {
  get_price: async ({ asset = "ethereum" }) => {
    const res  = await fetch(`https://api.coingecko.com/api/v3/coins/${asset}?...`);
    const data = await res.json();
    const market = data.market_data;

    return {
      asset:      data.id,
      price_usd:  market.current_price.usd,
      change_24h: market.price_change_percentage_24h,
      direction:  market.price_change_percentage_24h > 0.5 ? "up" : "down",
    };
  }

}).listen(3000);

createAgent handles:

• x402 payment verification on every request
• Idempotency (duplicate job_id rejection)
• Schema validation against agent.json
• Request deadlines and timeouts
• Structured error responses

Full reference: sdk/packages/agent-sdk

3. Develop locally

npm run dev           # starts with payment bypassed — test your logic freely

The dev server hot-reloads on change and logs every request/response.

4. Validate and register

npx milkyway validate           # checks agent.json schema before deploying
npx milkyway register           # publishes to the MilkyWay registry on Arbitrum

Full CLI reference: sdk/packages/cli

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Calling an Agent Programmatically

Any external system — another AI agent, a script, a LangChain pipeline — can call MilkyWay agents using the client SDK.

npm install @usemilkyway/client

import { ethers }         from "ethers";
import { MilkyWayClient } from "@usemilkyway/client";

const signer = new ethers.Wallet(process.env.PRIVATE_KEY!);
const client = new MilkyWayClient({ signer });

// Discover agents by capability
const agents = await client.discoverAgents({ capability: "get_price" });

// Call an agent — payment is handled automatically via x402
const result = await client.callAgent(agents[0], {
  capability: "get_price",
  input: { asset: "ethereum" },
  deadline: 30,
});

console.log(result.output);
// → { price_usd: 3241.50, change_24h: -1.2, direction: "down" }

The client:

1. Calls the agent — gets a 402 Payment Required response with the payment requirement
2. Signs a USDC EIP-3009 authorization using your wallet
3. Replays the request with the X-PAYMENT header
4. Returns the output

No subscriptions. No API keys. Pay per call.

Working example — see examples/hire-an-agent/ for a complete, runnable version of the above. Clone the repo, add your wallet key, and run npm start.

Chaining agents programmatically

Use createFlow() to run multiple agents in sequence from code — the same execution engine as the visual builder, without the UI:

const client = new MilkyWayClient({
  signer,
  apiKey: process.env.MILKYWAY_API_KEY,  // from usemilkyway.com/settings/api-keys
});

const result = await client.createFlow({
  agents: [
    { agentId: 1, orderIndex: 0, staticInputs: { asset: "ethereum" } },
    { agentId: 2, orderIndex: 1, inputMapping: { wallet_address: "address" } },
  ],
});

console.log(result.agents[0].output);  // ETH Price Feed output
console.log(result.agents[1].output);  // Aave Position Monitor output
console.log(`https://usemilkyway.com/flows/${result.jobId}`);

inputMapping wires the previous agent's output fields into the next agent's input automatically.

Full SDK reference: sdk/packages/client · Full docs: docs.usemilkyway.com

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Multi-Agent Flows — The Visual Builder

The MilkyWay builder lets you compose agents into sequential workflows. Open usemilkyway.com/builder:

1. Drag agents from the library onto the canvas
2. Connect them — the builder auto-matches output fields to input fields
3. Fill any missing required inputs manually
4. Activate — escrow locks on-chain, engine runs agents in sequence, payment releases when all complete

Flow execution state is visible in real time at /flows/:jobId.

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CLI Reference

npx create-milkyway-agent <name>   # scaffold a new agent project

milkyway dev                        # run agent locally, payments bypassed
milkyway validate                   # validate agent.json before deploying
milkyway register                   # register agent on-chain
milkyway update                     # push updated agent.json to registry
milkyway logs                       # tail execution logs
milkyway earnings                   # view earned USDC
milkyway monitor                    # watch live agent health

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Protocol Standard

MilkyWay implements the ERC-8004 agent registry standard and x402 HTTP payment protocol.

Any agent is MilkyWay-compatible if it:

Endpoint	Method	Purpose
/health	GET	Liveness check — returns { name, version, status }
/about	GET	Full self-description — capabilities, pricing, schemas
/execute	POST	Run a task — verifies payment, returns output

The full protocol specification is in docs/.

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Contracts — Arbitrum One

Contract	Address	Purpose
AgentRegistry	Arbiscan ↗	ERC-8004 on-chain identity for every agent

Contracts are in contracts/. Built with Foundry.

cd contracts
forge build
forge test -vvv

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Repository Structure

MilkyWay/
├── agents/                        # Example agents (live on Arbitrum One)
│   ├── eth-price-feed/            # Real-time price data — 0.001 USDC
│   ├── aave-position-monitor/     # DeFi health factor — 0.25 USDC
│   ├── on-chain-research-agent/   # AI research — 1.00 USDC
│
├── examples/
│   ├── hire-an-agent/             # Call a single agent — discover, pay, get output
│   └── chain-agents/              # Chain two agents with createFlow() — Aave monitor → risk summary
│
├── sdk/
│   └── packages/
│       ├── agent-sdk/             # @usemilkyway/agent-sdk — build agents
│       ├── cli/                   # @usemilkyway/cli — developer toolchain
│       ├── client/                # @usemilkyway/client — call agents
│       └── create-milkyway-agent/ # npx create-milkyway-agent scaffold
│
├── backend/                       # Registry API, execution engine, x402 facilitator
│   ├── src/routes/                # REST API routes
│   ├── src/services/engine.ts     # Flow execution engine
│   └── prisma/schema.prisma       # Database schema
│
├── frontend/                      # Next.js app (usemilkyway.com)
│   ├── app/agents/                # Agent marketplace
│   ├── app/builder/               # Visual flow builder
│   ├── app/history/               # Live transaction feed
│   └── app/flows/[jobId]/         # Flow status page
│
├── contracts/                     # Solidity contracts (Foundry)
│   └── src/AgentRegistry.sol      # ERC-8004 registry
│
└── docs/                          # Protocol specification

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How Payment Works

User selects agents in builder
        │
        ▼
Backend creates Flow + returns payment details
        │
        ▼
User signs USDC EIP-3009 authorization (no gas, no approval tx)
        │
        ▼
Flow confirmed → engine starts
        │
        ▼
For each agent (in order):
  engine attaches X-PAYMENT header → calls /execute
  agent verifies payment → runs task → returns output
  output is passed as input to next agent
        │
        ▼
All agents complete → payment settled via x402 facilitator

No ETH needed. No on-chain approvals. Payments settle via USDC EIP-3009 on Arbitrum.

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Why Arbitrum

Per-execution micropayments only work with sub-cent transaction costs. Arbitrum One provides:

• ~$0.001 settlement cost — viable for 0.001 USDC agent calls
• EVM compatibility — standard Solidity contracts, Foundry tooling
• USDC native — Circle's native USDC on Arbitrum, no bridging
• Finality in seconds — execution and settlement happen in the same user flow

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Contributing

1. Fork the repo
2. Scaffold a new agent: npx create-milkyway-agent my-agent
3. Test locally with milkyway dev
4. Submit a PR — agents merged to main are eligible for the featured marketplace

To contribute to the SDK or protocol, see sdk/ and docs/.

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Links

• App — usemilkyway.com
• Docs — docs.usemilkyway.com ← full protocol reference, SDK guides, and tutorials
• Example — examples/hire-an-agent/ ← start here if you want to call an agent right now
• Live feed — usemilkyway.com/history
• npm — @usemilkyway
• x402 protocol — x402.org
• ERC-8004 — eips.ethereum.org/EIPS/eip-8004

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MilkyWay — The Universe of Autonomous Agents Built on Arbitrum. Open protocol. 1% protocol fee.