payagent

payagent

Let AI agents pay for APIs. The ArisPay SDK + CLI for x402 USDC payments.

Two ways to pay:

• Delegated custody — ArisPay provisions a Coinbase CDP-managed wallet and signs on your agent's behalf. No private key ever lives in your process, and ArisPay enforces per-transaction, daily, monthly, and allowed-domain limits server-side.
• Local signer (permissionless) — payFetchLocal({ privateKey }) signs EIP-3009 payments in your process with any funded key. No ArisPay account, no API key, no provisioning — npm install payagent is the whole setup. Settlement runs through whatever facilitator the seller uses (any upstream-compatible x402 facilitator, including facilitator.arispay.app — source).

Honest trade-off: spend limits, domain allowlists, suspension, and the payment feed are server-side features of the delegated model and do not exist in local-signer mode — the only guardrail is an optional client-side per-transaction cap. Use a dedicated low-balance wallet for local signing.

Install

npm install payagent

Requires Node.js >= 18.

Quick start (local signer — no ArisPay account)

Point the CLI at any funded EOA key and pay in one step — nothing else to set up:

PAYAGENT_PRIVATE_KEY=0x… npx payagent pay https://api.example.com/premium

Library equivalent:

import { payFetchLocal } from "payagent";

const fetch402 = payFetchLocal({
  privateKey: process.env.PRIVATE_KEY!,
  maxPerTxBaseUnits: "1000000", // optional client-side cap: $1.00 USDC
});
const res = await fetch402("https://api.example.com/premium");

The vercel and langchain tool integrations accept either mode — pass { privateKey } for local signing or { arispayUrl, apiKey } for delegated.

Quick start (CLI)

One command. No dashboard trip, no separate init, no separate agent create, no manual funding step.

npx payagent pay https://api.example.com/premium

On a cold machine, pay self-bootstraps in order:

• Auth — prints a verification URL + code (OAuth device-code flow). Open it, approve, the CLI picks up your API key.
• Agent — auto-creates a local agent named default with conservative defaults ($5/tx, $20/day, $100/month, Base mainnet, URL hostname allowlisted). Persisted to ~/.payagent/config.json, so subsequent runs skip this step.
• Funding — if the agent has 0 USDC, prints a Coinbase Onramp link (or the raw wallet address if onramp isn't configured on the deployment) and polls until funds land.
• Pay — retries the URL with a signed X-PAYMENT header.

Progress goes to stderr; the HTTP response body is written to stdout, so you can pipe it:

npx payagent pay https://api.example.com/premium | jq .

Overrides (all optional) let you tune the first-run defaults:

npx payagent pay <url> \
  --agent hermes \                        # name the agent (defaults to `default`)
  --per-tx 0.50 --daily 10 --monthly 100 \# dollars; cents stored server-side
  --network base \                        # base | base-sepolia | ethereum | polygon
  --domains api.example.com,api.example.net \
  --method POST --body '{"foo":"bar"}' \
  --amount 25                             # preset Coinbase Onramp amount (USD)

For advanced setups you can still run the gates manually:

npx payagent init                                     # OAuth device-code sign-in
npx payagent agent create --name hermes \
  --per-tx 0.50 --daily 10 --monthly 100              # amounts in dollars
npx payagent agent fund hermes --hosted 25            # Coinbase Onramp link for $25

The CLI and the @arispay/payagent-mcp server share the same ~/.payagent/config.json, so an agent created on the command line is immediately available to Claude Desktop or any other MCP host.

Quick start (programmatic)

import { launchAgent } from 'payagent';

const hermes = await launchAgent({
  name: 'hermes',
  limits: { perTx: 50, daily: 1000, monthly: 10000 }, // cents
  allowedDomains: ['api.example.com'],
});

console.log(`Fund this wallet with USDC on Base: ${hermes.walletAddress}`);
await hermes.waitUntilFunded();

const res = await hermes.fetch('https://api.example.com/premium');
const data = await res.json();

For finer-grained control, the low-level DelegationClient + payFetchDelegated primitives are still exported and used by launchAgent under the hood:

import { DelegationClient, payFetchDelegated } from 'payagent';

const client = new DelegationClient('https://api.arispay.app', process.env.ARISPAY_API_KEY);
const agent = await client.createX402Agent({
  name: 'my-agent',
  maxPerTx: 100,
  maxDaily: 1000,
  maxMonthly: 10000,
  allowedDomains: ['api.example.com'],
});
await client.pollUntilFunded(agent.agentId);

const fetch402 = payFetchDelegated({
  arispayUrl: 'https://api.arispay.app',
  apiKey: agent.apiKey,
});
const res = await fetch402('https://api.example.com/premium');

CLI reference

Command	Purpose
payagent init	Browser-based OAuth device-code flow. Saves the developer API key to ~/.payagent/config.json (mode 0600).
payagent status / payagent doctor	Show local readiness: API target, key validity, cached agents, balances, and next command.
payagent whoami	Show the current developer key prefix, base URL, and config path.
payagent logout	Clear the developer key. Local agent records are kept.
`payagent agent create --name N --per-tx N --daily N --monthly N [--domains a,b] [--network base	base-sepolia
payagent agent fund NAME	Print the funding address, render a QR, and poll until the wallet first receives USDC.
payagent agent balance NAME	Show current balance + fundedAt.
payagent agent list	List locally-cached agents.
payagent agent remove NAME	Drop an agent from the local cache (the server-side agent remains).
payagent pay URL [--agent N] [--method GET/POST/…] [--body STR]	Make a single paid request through payFetchDelegated.

Amounts on the CLI are in dollars (5, 5.00, or "$5.00" all mean 500 cents). Internally everything is integer cents, matching the ArisPay API.

Env overrides respected everywhere: ARISPAY_API_KEY, ARISPAY_URL, PAYAGENT_CONFIG_DIR.

Hosted top-up (Coinbase Onramp)

For end-user-friendly funding — no crypto wallet required — ArisPay can return a hosted Coinbase Onramp URL instead of a raw wallet address. The user opens the URL, pays with card or Apple Pay, and Coinbase deposits USDC straight into the agent's CDP wallet.

import { launchAgent, HostedTopupNotConfiguredError } from 'payagent';

const hermes = await launchAgent({
  name: 'hermes',
  limits: { perTx: 50, daily: 1000, monthly: 10000 },
});

try {
  const link = await hermes.getFundingLink({ amount: 50 });
  console.log(`Pay here: ${link.fundingUrl}`);
  // Expires at link.expiresAt, valid for ~2 hours.
  await hermes.waitUntilFunded();
} catch (err) {
  if (err instanceof HostedTopupNotConfiguredError) {
    // Deployment hasn't set ARISPAY_ONRAMP_PROVIDER — fall back to
    // the plain wallet address.
    console.log(`Send USDC on base to ${hermes.walletAddress}`);
    await hermes.waitUntilFunded();
  } else {
    throw err;
  }
}

Or via the CLI:

npx payagent agent fund hermes --hosted 50

Requires ARISPAY_ONRAMP_PROVIDER=coinbase + COINBASE_ONRAMP_APP_ID on the API deployment. Without them, the --hosted flag falls back to the manual path with a clear message.

How x402 works

The x402 protocol uses HTTP status code 402 for machine-to-machine API payments:

• Server returns 402 Payment Required with payment requirements (chain, amount, recipient).
• payagent asks ArisPay to sign an EIP-3009 transferWithAuthorization — a gasless USDC transfer authorization.
• ArisPay validates the request against your delegation limits (maxPerTx, maxDaily, maxMonthly, allowedDomains), then signs via the CDP-managed wallet.
• payagent retries the request with the signed payment in the X-PAYMENT header.
• Server's facilitator submits the authorization on-chain and returns the API response.

Key properties:

• No private keys in your agent — the signing key lives in Coinbase CDP, never in your process.
• Server-enforced limits — ArisPay rejects requests that breach your delegation before signing.
• No gas fees for agents — the seller's facilitator sponsors gas.
• USDC stablecoins — amounts are in dollars, no price volatility.

API

DelegationClient — provision and monitor agents

const client = new DelegationClient('https://api.arispay.app', process.env.ARISPAY_KEY);

const agent = await client.createX402Agent({
  name: 'hermes-prod',
  agentType: 'hermes',
  maxPerTx: 100,       // cents
  maxDaily: 1000,
  maxMonthly: 10000,
  allowedDomains: ['api.example.com'],
  network: 'base',     // default
});
// agent.agentId, agent.walletAddress, agent.apiKey (returned ONCE)

// Wait for the wallet to be funded with USDC.
await client.pollUntilFunded(agent.agentId);

// Or check manually:
const balance = await client.getBalance(agent.agentId);
// { walletAddress, usdcBalance, network, fundedAt }

Supported network values: base (default, mainnet), base-sepolia, ethereum, polygon.

The apiKey returned by createX402Agent is the credential for this agent only — ArisPay stores only its SHA-256 hash and cannot recover it. Store it securely.

payFetchDelegated(config) — drop-in fetch

const fetch402 = payFetchDelegated({
  arispayUrl: 'https://api.arispay.app',
  apiKey: agent.apiKey,
});
const res = await fetch402('https://api.example.com/data');

Works like native fetch. On 402, payagent asks ArisPay to sign via CDP, then retries. If ArisPay rejects (limit breach, disallowed domain, etc.), throws PaymentRejectedError.

getUSDCBalance(address, chain?, rpcUrl?) — direct on-chain read

import { getUSDCBalance, formatUSDC } from 'payagent';

const raw = await getUSDCBalance(agent.walletAddress);           // default chain: 'base'
const raw2 = await getUSDCBalance(agent.walletAddress, 'base');
console.log(formatUSDC(raw), 'USDC');

Utility that reads USDC balance directly from any EVM RPC — handy for sanity-checking wallet state independent of ArisPay's balance endpoint.

Supported chains

Chain	Network ID	Notes
Base	eip155:8453	Default — mainnet, lowest fees
Base Sepolia	eip155:84532	Testnet
Ethereum	eip155:1	Mainnet
Polygon	eip155:137	Mainnet

Errors

import {
  PaymentRejectedError,     // ArisPay denied signing, or server returned 402 after payment
  InvalidRequirementsError, // Could not parse the 402 response
  PayAgentError,            // Base class
} from 'payagent';

Framework integrations

Vercel AI SDK

import { createPayAgentTool } from 'payagent/vercel';
import { generateText } from 'ai';

const payTool = createPayAgentTool({
  arispayUrl: 'https://api.arispay.app',
  apiKey: process.env.ARISPAY_AGENT_KEY,
});

const { text } = await generateText({
  model: yourModel,
  tools: { pay_api: payTool },
  prompt: 'Get the premium forecast from https://weather-api.example.com/forecast',
});

Requires peer dependencies: ai, zod.

LangChain

import { createPayAgentTool } from 'payagent/langchain';

const payTool = createPayAgentTool({
  arispayUrl: 'https://api.arispay.app',
  apiKey: process.env.ARISPAY_AGENT_KEY,
});

Requires peer dependency: @langchain/core.

MCP server

Use @arispay/payagent-mcp to add payment capabilities to Claude Desktop, Cursor, or any MCP client.

Migrating from 1.x

v2 removes the self-custody path (payFetch, PayAgent, raw private-key signing). ArisPay's product is delegated-custody only — keys live in Coinbase CDP with server-enforced limits.

Migration:

• Replace payFetch({ privateKey }) with payFetchDelegated({ arispayUrl, apiKey }).
• Replace new PayAgent({ privateKey, budget, maxPerRequest }) with DelegationClient.createX402Agent({ maxPerTx, maxDaily, maxMonthly, ... }) to provision, then payFetchDelegated to transact.
• BudgetExceededError, UnsupportedChainError, and DomainNotAllowedError are gone — their equivalents are now server-side rejections surfaced as PaymentRejectedError.

License

MIT