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x402 is Allium’s micropayment protocol for blockchain data. AI agents and developers pay per API call with USDC — no API key, no registration, no subscription. Just a wallet and USDC.

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Key Benefits

No API Key

No registration or key management. Your wallet is your identity.

Pay Per Call

Only pay for what you use. Prices start at $0.001 per request.

Agent-Native

Built for AI agents — autonomous payments with no human in the loop.

Gasless Payments

Allium handles onchain settlement. Users only need USDC, not ETH.

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How It Works

The x402 protocol uses HTTP status code 402 Payment Required to negotiate payments inline with API requests.
1

Send request

Make a normal API request to any x402-enabled endpoint.
2

Receive 402

The server responds with 402 Payment Required and accepts array of payment options.
3

Sign payment

Your client constructs and signs an EIP-712 payment authorization via Privy server wallets — no private keys or gas needed.
4

Retry with signature

Resend the original request with the payment signature header attached.
5

Settlement

Allium verifies the authorization and settles the USDC payment onchain via Coinbase.
6

Get data

Payment confirmed — you receive your data with a 200 response.
The quickstart shows how to set this up with Privy server wallets in a few lines of Python. You send a request, and the helper handles the payment flow.

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Supported Tokens & Networks

x402 payments use USDC on the following networks:
NetworkUSDC Contract AddressEIP-712 Domain
Base (mainnet)0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913name: USD Coin, version: 2
Base Sepolia (testnet)0x036CbD53842c5426634e7929541eC2318f3dCF7ename: USDC, version: 2
Getting started? Use Base Sepolia with testnet USDC first. You can get testnet USDC from Circle’s faucet.

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MCP vs x402

Allium offers two ways for agents to access blockchain data. Choose based on your setup:
MCPx402
ProtocolModel Context Protocol (tool calls)REST API with micropayments
AuthOAuth or API keyUSDC wallet (Base or Base Sepolia)
Best forAI coding assistants (Claude Code, Cursor)Autonomous agents, scripts, backends
SetupAdd MCP server to your clientInstall Python library + fund wallet
BillingAllium account / subscriptionPay-per-call, no account needed
Rate limitsPer account plan3/s data, 5/s docs (per wallet)
Use MCP if you’re working inside an AI coding assistant like Claude Code or Cursor. Use x402 if you’re building autonomous agents or backend services that need to pay for data programmatically.

Quickstart

Get your first x402 request working in under 5 minutes

Endpoints & Pricing

All x402-enabled endpoints, pricing, and rate limits

MCP Overview

Allium’s MCP server for AI coding assistants