Vercel AI SDK

Safety checks for AI SDK agents that pay

presign-guard-ai-sdk gives an AI SDK agent four tools to call before it signs or pays. The tools only check: they never sign, pay or move anything themselves. They work with AI SDK 5, 6 and 7.

Install

npm install presign-guard-ai-sdk ai zod

Try it without a wallet

With no payment set up, the token, signing and endpoint checks answer with the free quick check: the verdict only, a few per hour, marked free: true.

import { generateText, isStepCount } from 'ai';
import { fizzlTools } from 'presign-guard-ai-sdk';

const { text } = await generateText({
  model: 'anthropic/claude-sonnet-5.5',
  tools: fizzlTools(),
  prompt:
    'Is USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base safe to buy, ' +
    'and is https://ichimoku-signal.fizzl.eu/signal/BTC-USDT safe to pay?',
  stopWhen: isStepCount(5),
});

console.log(text);

The tools

Tool	What it checks	Full check	Free quick check
`check_before_signing`	A transaction, token approval or signature (permit, Permit2) before signing: drainers, unlimited approvals, look-alike dapps. Green / orange / red with reasons.	$0.01	verdict only
`check_token`	A token before buying, holding or accepting it: honeypots, rug-pull signs, look-alikes. Solana and EVM chains.	$0.01	verdict and grade
`check_wallet_approvals`	Every open token approval of an EVM wallet, and which ones to revoke.	$0.02	none
`check_endpoint_before_paying`	An x402 or MPP paid API before paying it: go / caution / no_go, the cheapest option that settles, budget, track record, bait signs.	$0.001	go / caution / no_go with the problems found

Pick some with fizzlTools({ only: ['check_endpoint_before_paying'] }). A failed check comes back as { error, message }, so the model can tell its user; it is never thrown.

The full checks: pay per call over x402

Give the tools an x402-paying fetch. The agent pays each check in USDC on Base from its own wallet.

import { generateText, isStepCount } from 'ai';
import { wrapFetchWithPayment, x402Client } from '@x402/fetch';
import { ExactEvmScheme } from '@x402/evm/exact/client';
import { privateKeyToAccount } from 'viem/accounts';
import { fizzlTools } from 'presign-guard-ai-sdk';

// A check never costs more than $0.02: cap every payment.
const payer = new x402Client().setSpendControls({ maxAmountPerPayment: '$0.02' });
payer.register('eip155:8453', new ExactEvmScheme(privateKeyToAccount(process.env.AGENT_KEY)));

const { text } = await generateText({
  model: 'anthropic/claude-sonnet-5.5',
  tools: { ...fizzlTools({ fetch: wrapFetchWithPayment(fetch, payer) }), ...yourOtherTools },
  system:
    'Before you pay any API, call check_endpoint_before_paying. Before you sign anything, ' +
    'call check_before_signing. Never continue on red or no_go.',
  prompt: 'Buy the BTC funding rate from https://api.example.com/funding for at most $0.05',
  stopWhen: isStepCount(8),
});

Or prepaid credits

Buy a pack once (presign-guard: 100 checks for $0.80; x402 Doctor: 1000 preflights for $0.80), then pass the keys:

fizzlTools({ creditKeys: { presign: process.env.PRESIGN_CREDIT_KEY, doctor: process.env.DOCTOR_CREDIT_KEY } });

Options

Option	Default
`fetch`	global fetch	An x402-paying fetch, or plain fetch with credit keys
`creditKeys`	none	`{ presign, doctor }`, sent as `x-credit-key`
`only`	all four	Tool names to include
`free`	`true`	Fall back to the free quick check when a check can't be paid
`timeoutMs`	30000	Per check

npm: presign-guard-ai-sdk · source on GitHub
Python and LangChain: pip install fizzl
Want the wallet to stop the agent itself, not just tell the model? The Fizzl agent wallet