P402 Protocol

AI payment router. Route across 300+ models, pay per request in USDC on Base.

P402 sits between your AI application and every LLM provider. It handles intelligent multi-provider routing (cost / quality / speed / balanced), on-chain micropayment settlement via the x402 protocol (gasless USDC on Base), and spending guardrails for autonomous agents.

Why P402

Quick Start (VS Code / Cursor / Windsurf)

Install the extension — the MCP server is embedded, tools appear in Copilot agent mode immediately, no config files required:

ext install p402-protocol.p402

Then run P402: Configure API Key from the command palette.

→ VS Code Marketplace · Open VSX

Quick Start (Claude Desktop / any MCP client)

{
  "mcpServers": {
    "p402": {
      "command": "npx",
      "args": ["-y", "@p402/mcp-server"],
      "env": { "P402_API_KEY": "p402_live_..." }
    }
  }
}

→ MCP docs · MCP Registry

Quick Start (SDK)

npm install @p402/sdk

import P402Client from '@p402/sdk';

const p402 = new P402Client({ apiKey: process.env.P402_API_KEY });

// Drop-in OpenAI replacement — P402 picks the best provider
const response = await p402.chat({
  messages: [{ role: 'user', content: 'Explain x402 payments in one sentence.' }],
  p402: { mode: 'cost' }   // cost | quality | speed | balanced
});

console.log(response.choices[0].message.content);
// p402_metadata: { provider: 'deepseek', cost_usd: 0.00031, latency_ms: 412 }

Quick Start (CLI)

# Authenticate once
npx p402 login

# Chat using the cheapest provider
npx p402 chat "What is x402?" --mode cost

# Check facilitator health
npx p402 health

Routing Modes

Session Budgets

Enforce hard spending caps for autonomous agents:

// Create a $10 session — agent cannot spend a cent more
const session = await p402.createSession({ budget_usd: 10 });

// All chat requests are deducted from the session
const response = await p402.chat({
  messages,
  p402: { session_id: session.id, mode: 'cost' }
});

// Check remaining budget
const { budget } = await p402.getSession(session.id);
console.log(`$${budget.remaining_usd} remaining`);

x402 Payments

x402 is a machine-native payment protocol using HTTP 402. AI agents pay for resources using gasless EIP-3009 USDC transfers on Base L2.

Client → signs EIP-3009 authorization
       → POST /api/v1/facilitator/verify
       → POST /api/v1/facilitator/settle
Facilitator → executes transferWithAuthorization
            → pays gas (user pays zero gas)
            → returns { success, txHash, receipt }

Network: Base Mainnet (Chain ID: 8453) · Asset: USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913

→ x402 payments guide

A2A Protocol

P402 implements the Google A2A spec over JSON-RPC 2.0. Agents communicate through structured tasks, discover capabilities via /.well-known/agent.json, and settle payments via the x402 extension.

// Discover P402's capabilities
GET https://p402.io/.well-known/agent.json

// Submit a task
POST https://p402.io/api/a2a
{ "jsonrpc": "2.0", "method": "tasks/send", "params": { ... } }

→ A2A protocol guide

Packages

Package	Description	Version
@p402/sdk	TypeScript SDK — P402Client, types, EIP-712 mandate helpers
@p402/cli	CLI tool — login, chat, sessions, mandates, analytics
@p402/mcp-server	stdio MCP server — 6 tools over Model Context Protocol
p402 VS Code extension	Embedded MCP server for VS Code, Cursor, and Windsurf — zero config

Examples

Docs

Community

• Dashboard: p402.io/dashboard
• Docs: p402.io/docs
• Issues: GitHub Issues
• Security: See SECURITY.md for responsible disclosure
• Contributing: See CONTRIBUTING.md

License

MIT © P402 Protocol