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What is A2A?

A2A (Agent-to-Agent) is a JSON-RPC 2.0 based protocol that enables AI agents to discover and communicate with each other. Snack Money implements A2A with the X402 extension, combining agent discovery with cryptocurrency payments.

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Key Features

  • Agent Discovery - Automatic service discovery via agent cards
  • JSON-RPC 2.0 - Standard protocol for agent communication
  • X402 Extension - Integrated crypto payment capabilities
  • Multi-Network - Support for both Base and Solana networks
  • Task-Based Flow - Asynchronous payment processing
  • 6 Payment Platforms - Twitter, Farcaster, GitHub, Email, Web, Instagram

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How A2A Works with Snack Money

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1. Discovery Phase

Agents discover Snack Money’s capabilities through the agent card: 
GET https://api.snack.money/a2a/.well-known/agent-card
The agent card describes:
  • Available payment skills (e.g., snack-money.pay.twitter)
  • Required parameters and schemas
  • Supported X402 extension

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2. Payment Request

Agents send JSON-RPC requests to initiate payments: 
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "snack-money.pay.twitter",
  "params": {
    "receiver": "username",
    "amount": 0.01,
    "description": "Payment via A2A",
    "meta": {
      "agent_name": "my-agent"
    }
  }
}

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3. Payment Requirements

Snack Money responds with payment requirements: 
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "taskId": "task_abc123",
    "status": "PAYMENT_REQUIRED",
    "payment": {
      "network": "eip155:8453",
      "amount": "10000",
      "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "recipient": "0x..."
    }
  }
}

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4. On-Chain Payment

The agent executes the USDC transfer on the specified network (Base or Solana).

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5. Payment Proof Submission

After blockchain confirmation, the agent resubmits with proof: 
{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "snack-money.pay.twitter",
  "params": {
    "receiver": "username",
    "amount": 0.01,
    "taskId": "task_abc123",
    "payment": {
      "network": "eip155:8453",
      "transactionHash": "0x..."
    }
  }
}

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6. Completion

Snack Money verifies the payment and returns success: 
{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "taskId": "task_abc123",
    "status": "PAYMENT_CONFIRMED",
    "metadata": {
      "x402:transactionId": "1234567890",
      "x402:receipt": "https://snack.money/x/username?txn=1234567890"
    }
  }
}

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Available Skills

Snack Money exposes the following A2A skills:

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Single Payments

  • snack-money.pay.twitter - Send to Twitter/X users
  • snack-money.pay.farcaster - Send to Farcaster users
  • snack-money.pay.github - Send to GitHub users
  • snack-money.pay.email - Send to email addresses
  • snack-money.pay.web - Send to web domains
  • snack-money.pay.instagram - Send to Instagram users

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Batch Payments

  • snack-money.batch-pay.twitter - Batch payments to Twitter users
  • snack-money.batch-pay.farcaster - Batch payments to Farcaster users
  • snack-money.batch-pay.github - Batch payments to GitHub users
  • snack-money.batch-pay.email - Batch payments to email addresses
  • snack-money.batch-pay.web - Batch payments to web domains
  • snack-money.batch-pay.instagram - Batch payments to Instagram users

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Required Headers

When making A2A requests, include: 
Content-Type: application/json
X-A2A-Extensions: https://a2a.dev/spec/extensions/x402/v0

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Network Support

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Base (EVM)

  • Network ID: eip155:8453
  • Token: USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913)
  • Use EVM private key for signing

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Solana (SVM)

  • Network ID: solana:mainnet
  • Token: USDC SPL token
  • Use Solana private key for signing

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Integration Example

For complete working examples, see the A2A Examples page or check out the snack-money-examples/a2a repository.

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Why A2A + X402?

The combination of A2A and X402 protocols provides:
  1. Agent Interoperability - Agents can discover and use services automatically
  2. Payment Integration - Native crypto payments without manual setup
  3. Standardized Communication - JSON-RPC 2.0 ensures compatibility
  4. Decentralized - No central authority or intermediary required
  5. Multi-Chain - Support for different blockchain networks

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