StreamFlow: Autonomous API Marketplace for AI Agents

The First x402 Implementation on Polygon — Enabling AI agents to autonomously discover and pay for APIs using Coinbase's x402 protocol on Polygon's payment-optimized infrastructure.

🎯 One-Liner

"Stripe for AI Agents on Polygon — where autonomous agents pay per API call using x402 micropayments, settled in USDC on the world's leading payments blockchain."

🎯 Executive Summary

The Problem

AI agents are the future of software, but they're stuck in Web2 payment rails:

🚫 Can't manage API keys or credit cards
💸 Fixed subscriptions waste money on variable usage
🏢 Centralized platforms take 30% cuts
🔍 No way to autonomously discover services

Market Gap: The AI agent economy needs decentralized, usage-based payment infrastructure.

Our Solution

StreamFlow implements Coinbase's x402 payment protocol on Polygon, enabling:

✅ Agent-to-Agent Commerce: Zero human intervention
✅ Pay-Per-Token Pricing: As low as $0.00001/token
✅ Decentralized Verification: Chainlink CRE prevents fraud
✅ Open Marketplace: Any API provider can monetize
✅ Polygon Settlement: Leverage $3.6B stablecoin liquidity

Key Innovation

"StreamFlow proves x402 is a truly open protocol by implementing it on Polygon, demonstrating how Coinbase's payment standard can enable the AI agent economy across any EVM chain while leveraging Polygon's payment-optimized infrastructure."

Technical Achievement:

First x402 marketplace implementation
First x402 deployment on Polygon
First AI agent payment system with CRE verification

🌟 Why Polygon + x402?

The Perfect Match

Requirement	Polygon Solution	x402 Solution
High Transaction Volume	5,000 TPS (Rio upgrade)	HTTP-native (no blockchain bloat)
Low Costs	~$0.005/tx	Micropayments viable
Stablecoin Liquidity	$3.6B USDC/USDT	Native USDC support
Agent-Friendly	Fast finality (5 sec)	No API keys required
Payment Leader	Stripe, Mastercard partners	Open payment standard

Result: AI agents can make thousands of micro-payments daily at costs lower than traditional payment processors.

👥 User Personas

Persona 1: "Maya" - The Agent Builder

Profile: Founder building autonomous customer service agents

Current Pain:

Agents need to consume multiple LLM APIs
OpenAI charges $20/month even if agents use $2
Can't switch providers without rewriting code

StreamFlow Solution:

# Agent automatically selects cheapest provider
cheapest_api = await marketplace.query(model_type="general")
response = await agent.call_api(cheapest_api, prompt="...")
# Pays $0.0045 (150 tokens × $0.00003) instead of $20/month

Impact: 98% cost reduction through usage-based pricing

Persona 2: "Raj" - The AI API Provider

Profile: ML engineer with fine-tuned legal analysis model

Current Pain:

Can't compete with OpenAI's distribution
Stripe takes 2.9% + $0.30 per transaction
Model sits idle 80% of the time

StreamFlow Solution:

// Register API in marketplace
marketplace.registerService(
    endpoint="https://legal-ai.com/api",
    pricePerToken=0.00005 * 1e6  // $0.00005 USDC
);
// Earn $0.005 per request, settled instantly on Polygon

Impact: Earn from 1,000 micro-transactions vs 5 enterprise customers

⚡ Core Features

1. x402 Protocol on Polygon

What: HTTP-native payment protocol adapted for Polygon's ecosystem

How It Works:

POST /api/v1/generate HTTP/1.1
Host: api.streamflow.xyz
Content-Type: application/json
X-Payment-Auth: polygon-0x742d35Cc...

HTTP/1.1 402 Payment Required
X-Payment-Required: 0.003 USDC
X-Payment-Address: 0x742d35Cc6634C0532925a3b844Bc454e4438f44e

[Agent pays via CDP wallet]

HTTP/1.1 200 OK
Content-Type: application/json
X-Tokens-Used: 150
X-Cost-USDC: 0.0045

{"text": "Quantum computing uses..."}

Innovation: First x402 implementation showing protocol extensibility beyond Base

2. CDP Server Wallets for Agents

What: Production-grade wallets with <200ms signing latency

Agent Onboarding:

import { Coinbase } from "@coinbase/coinbase-sdk";

// Create wallet on Polygon (zero human steps)
const wallet = await Coinbase.createWallet({
  networkId: "polygon-amoy"
});

// Set spending policy
await wallet.setPolicy({
  maxAmountPerTx: "10_000000", // 10 USDC
  allowedRecipients: [providerAddress]
});

Why Not Regular Wallets?

No seed phrases to manage
Sub-200ms transaction signing
Built-in policy controls
99.9% uptime SLA

3. Chainlink CRE Verification

What: Off-chain computation that prevents usage fraud

The Problem: How do you trust API providers report accurate usage?

The Solution:

1. API logs usage: "Agent_123 used 150 tokens"
2. CRE polls logs from multiple nodes (decentralized)
3. CRE calculates: 150 × $0.00003 = $0.0045 USDC
4. CRE triggers Polygon settlement with proof
5. Only verified payments settle on-chain

Gas Savings: $0.001 (CRE) vs $0.05+ (on-chain verification)

4. The Graph Analytics

What: Real-time dashboards querying Polygon events

Provider Dashboard:

query ProviderRevenue {
  providerStats(id: "0x742d35Cc...") {
    totalRevenue
    totalTokensServed
    uniqueAgents
    revenueByDay {
      date
      amount
    }
  }
}

Agent Dashboard:

Spending by provider
Cost per request trends
Savings vs subscriptions

5. Open API Marketplace

What: Permissionless registry on Polygon

Any Provider Can:

Deploy their API endpoint
Register in smart contract ($0.005 gas)
Start earning USDC in minutes

Any Agent Can:

Query The Graph for services
Authorize spending once
Pay per actual usage

Network Effect: More providers → Better prices → More agents → More providers

🏗️ Technical Architecture

Tech Stack (All Polygon-Native)

Layer	Technology	Purpose
Settlement	Polygon PoS (Amoy)	All payments settle here
Payment Protocol	x402 (Custom)	HTTP-native authorization
Agent Wallets	CDP Server Wallets	Sub-200ms signing
Off-chain Compute	Chainlink CRE	Usage verification
Backend	Python FastAPI	Marketplace + routing
Mock Services	Python	2 LLM endpoints (demo)
Indexing	The Graph	Real-time queries
Frontend	React + ethers.js	Provider/agent dashboards
Agent Framework	AgentKit (Python)	Autonomous logic

📐 System Flow

┌─────────────────────────────────────────────────────────────┐
│                 STREAMFLOW ON POLYGON                        │
└─────────────────────────────────────────────────────────────┘

1. AGENT CREATION (CDP Server Wallets)
   ↓
   Wallet created on Polygon in <3 seconds
   Pre-funded with USDC from faucet

2. SERVICE DISCOVERY (The Graph)
   ↓
   Agent queries: "What LLMs are available?"
   Graph returns: GeneralGPT ($0.00003/token), LegalAI ($0.00005/token)

3. AUTHORIZATION (x402 on Polygon)
   ↓
   Agent approves $10 USDC spending to GeneralGPT provider
   Transaction settles on Polygon (~5 seconds)

4. API CALL (HTTP + x402 Headers)
   ↓
   POST /api/v1/generate
   Headers: X-Payment-Auth, X-Agent-Address
   Body: {"prompt": "Explain quantum computing"}

5. USAGE LOGGING (FastAPI Middleware)
   ↓
   API processes request → logs 150 tokens used
   Returns response + cost breakdown

6. VERIFICATION (Chainlink CRE)
   ↓
   CRE polls usage logs (every 30s)
   Multi-node consensus: "150 tokens confirmed"
   Calculates: 150 × $0.00003 = $0.0045 USDC

7. SETTLEMENT (Polygon Smart Contract)
   ↓
   CRE triggers: x402Contract.processPayment(agent, provider, 0.0045)
   USDC transfers on Polygon
   Event emitted: PaymentProcessed

8. ANALYTICS (The Graph)
   ↓
   Subgraph indexes PaymentProcessed event
   Dashboard updates in real-time
   Provider sees: +$0.0045 revenue
   Agent sees: -$0.0045 spent

9. WITHDRAWAL (Provider Action)
   ↓
   Provider calls: x402Contract.withdraw()
   USDC sent to provider's CDP wallet on Polygon

Every step happens on Polygon ✅

🚀 Quick Start

Prerequisites

node --version    # v18+
python --version  # 3.10+
forge --version   # Foundry for Solidity
gh --version      # GitHub CLI

Installation

# Clone repository
git clone https://github.com/yourusername/streamflow.git
cd streamflow

# Install dependencies
npm install
pip install -r requirements.txt

# Configure environment
cp .env.example .env
# Add your API keys:
# - CDP_API_KEY_NAME
# - CDP_API_KEY_SECRET
# - POLYGON_RPC_URL (https://rpc-amoy.polygon.technology)
# - GRAPH_API_KEY

Deploy Contracts (Polygon Amoy)

cd contracts
forge build
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $POLYGON_RPC_URL \
  --broadcast \
  --verify

Start Backend

cd backend
uvicorn main:app --reload --port 8000

Start Frontend

cd frontend
npm start

Test the Flow

# Terminal 1: Backend running
# Terminal 2: Run agent test
cd tests
python test_agent_flow.py

📁 Project Structure

streamflow/
├── contracts/              # Solidity smart contracts
│   ├── src/
│   │   ├── X402Payment.sol        # Main payment contract
│   │   ├── ServiceRegistry.sol    # API marketplace
│   │   └── interfaces/
│   │       └── IX402.sol          # x402 interface
│   ├── test/              # Foundry tests
│   └── script/            # Deployment scripts
│
├── cre-workflows/         # Chainlink CRE (TypeScript)
│   ├── src/
│   │   ├── usage-monitor.ts       # Polls API usage
│   │   ├── billing-calculator.ts  # Computes costs
│   │   └── settlement-trigger.ts  # Triggers Polygon tx
│   └── test/
│
├── backend/               # Python FastAPI
│   ├── main.py           # Marketplace API
│   ├── services/
│   │   ├── general_gpt.py        # Mock LLM 1
│   │   └── legal_ai.py           # Mock LLM 2
│   ├── middleware/
│   │   └── x402_auth.py          # Payment validation
│   └── tests/
│
├── subgraph/             # The Graph indexing
│   ├── schema.graphql    # Entity definitions
│   ├── subgraph.yaml     # Configuration
│   └── src/
│       └── mapping.ts    # Event handlers
│
├── frontend/             # React dashboard
│   ├── src/
│   │   ├── pages/
│   │   │   ├── ProviderDashboard.tsx
│   │   │   └── AgentDashboard.tsx
│   │   └── components/
│   │       ├── WalletConnect.tsx
│   │       └── PaymentHistory.tsx
│   └── public/
│
├── scripts/              # Utility scripts
│   ├── fund-wallets.ts   # USDC faucet helper
│   └── deploy-all.sh     # One-command deployment
│
└── docs/                 # Documentation
    ├── ARCHITECTURE.md
    ├── API.md
    └── DEPLOYMENT.md

🏆 Judging Criteria Alignment

Polygon Prize ✅

Category 1: x402 + AI/Agentic Application

✅ x402 protocol deployed on Polygon
✅ AI agents autonomously consume APIs
✅ All settlements on Polygon network
✅ High transaction volume potential

Category 2: x402 Protocol Expansion

✅ Adapts x402 for Polygon ecosystem
✅ Shows protocol extensibility beyond Base
✅ Custom facilitator logic for Polygon's stablecoin infrastructure

Category 3: Payment Flows

✅ Merchant application (API providers)
✅ Payment processing middleware
✅ Brings transaction count up (agent-driven volume)

Why We Win: First x402 implementation on Polygon proving the protocol works across any EVM chain

Coinbase Prize ✅

Core Requirements:

✅ CDP Server Wallets (agents + providers)
✅ x402 protocol implementation
✅ AgentKit integration (Python SDK)

Bonus Points:

✅ Using 3+ CDP products
✅ Novel x402 use case (marketplace)
✅ High-quality implementation
✅ Demonstrates protocol extensibility

Why We Win: Proves x402 is a truly open standard by implementing on non-Base chain

Chainlink Prize ✅

Core Functionality:

✅ CRE workflows for off-chain computation
✅ Decentralized usage verification
✅ Novel integration (CRE + x402)

Why We Win: First project combining CRE with x402 payments

The Graph Prize ✅

Requirements:

✅ Real-time analytics dashboards
✅ Complex queries (revenue aggregation)
✅ Essential to UX (service discovery)

Why We Win: Subgraph enables the entire marketplace discovery mechanism

🎬 Demo (5 Minutes)

Live Demo Flow

1. Provider Registration (30s)

# Connect CDP wallet
# Register "LegalAI" at $0.00005/token
# Show Polygon transaction: polygonscan.com/tx/0x...

2. Agent Discovery (30s)

# Query The Graph
{ apiServices { endpoint, pricePerToken } }
# Agent selects cheapest option

3. Automated Payment (1 min)

# Agent authorizes $10 USDC
# Makes API call → 402 response → pays → 200 response
# CRE settles on Polygon
# Show transaction on PolygonScan

4. Analytics Dashboard (1 min)

Provider view: +$0.0045 revenue (real-time)
Agent view: Cost comparison (saved 40%)

5. Impact Slide (30s)

First x402 on Polygon
98% cheaper than Stripe
Unlocks $X trillion agent economy

🤝 Contributing

We welcome contributions! See CONTRIBUTING.md

Development Workflow

git checkout -b feature/amazing-feature
git commit -m 'Add amazing feature'
git push origin feature/amazing-feature

📜 License

MIT License - see LICENSE

🔗 Links

Demo: streamflow-demo.vercel.app (coming soon)
Contracts: Polygon Amoy Explorer
Subgraph: The Graph Studio
Twitter: @StreamFlowAI

🙏 Acknowledgments

Built with:

Polygon - Payment-optimized blockchain
Coinbase CDP - Server Wallets & x402 protocol
Chainlink - CRE off-chain compute
The Graph - Decentralized indexing

Special thanks to ETH Global and all DevRel teams!

Built at ETH Global 2025 🚀
The first x402 implementation on Polygon
Empowering the autonomous agent economy

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