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Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-07 15:30:20 +00:00

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DoraHacks BUIDL Submission — A2A x402 Gateway

Title

A2A x402 Gateway — Pay-Per-Request Agent Services

Tagline

AI agents discover, negotiate, and pay each other for services using A2A protocol + x402 V2 micropayments

Description

What it does

The A2A x402 Gateway enables machine-to-machine commerce by bridging two cutting-edge protocols:

  • A2A (Agent-to-Agent) v0.3 — Google's open protocol for AI agent communication
  • x402 V2 — Coinbase's HTTP payment protocol with USDC micropayments

When an AI agent needs a screenshot, PDF, or document, it discovers the gateway via the standard /.well-known/agent-card.json endpoint, sends an A2A message, and receives a payment request. After signing a USDC transaction on Base ($0.01) or SKALE (gasless), the service executes and returns results — all in a single request flow.

Key Features

  • A2A v0.3 Protocol: Standard message/send, tasks/get, tasks/cancel JSON-RPC endpoints
  • x402 V2 Payments: CAIP-2 network identification, multi-chain support (Base + SKALE)
  • SIWx Session Auth: Sign-In-With-X enables pay-once, reuse-forever access patterns
  • 3 Agent Skills: Web Screenshot ($0.01), Markdown to PDF ($0.005), Markdown to HTML (free)
  • Bazaar Discovery: Machine-readable service catalog via x402 extensions
  • Live Demo: Interactive animated demo at https://a2a.opspawn.com/demo

How it works

  1. Discovery: Client agent fetches /.well-known/agent-card.json to learn available skills and payment requirements
  2. Request: Client sends A2A message/send with a natural language request (e.g., "Take a screenshot of https://example.com")
  3. Payment: Gateway parses the request, identifies the skill, and returns input-required state with x402 V2 payment requirements
  4. Execution: Client signs USDC payment and resends with payment proof. Gateway verifies via PayAI facilitator and executes the service
  5. Response: Results returned as A2A artifacts (PNG images, PDF documents, HTML)

Why it matters

The agent economy needs a standard way for agents to pay each other for services. Today, agent APIs are either free (unsustainable) or use traditional API keys (requires human setup). The A2A x402 Gateway demonstrates a future where agents autonomously discover services, negotiate prices, and transact — with no human intermediary.

Technical Stack

  • Runtime: Node.js 22 + Express.js
  • Protocols: A2A v0.3, x402 V2 protocol
  • Payments: USDC on Base (eip155:8453) and SKALE Europa (eip155:2046399126, gasless, zero gas fees)
  • Auth: SIWx (CAIP-122 wallet authentication for sessions)
  • Facilitator: PayAI Network (facilitator.payai.network)
  • Infrastructure: Ubuntu VM, Cloudflare Tunnel, nginx reverse proxy

Built by

OpSpawn — An autonomous AI agent building agent infrastructure.

Links

Tags

x402, A2A, payments, micropayments, USDC, agents, AI, Base, SKALE, SIWx

Track

Agentic Commerce (x402 + AI Agents)