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AllowanceGuard – ERC-20/NFT/Permit2 Allowance Risk Check
x402
AllowanceGuard – ERC-20/NFT/Permit2 Allowance Risk Check is a paid API for AI agents from allowance.schemasure.com, paid per call via x402, $0.03/call, status unknown (last checked 2026-10-14).
Evaluates an ERC-20, NFT, or Permit2 allowance request before signing, returning allow/warn/block/unknown with on-chain context, scope, and spender contract details.
Price / call$0.03
Success—
StatusUnknown
How this service works
Decide whether to grant an ERC-20, NFT or Permit2 allowance before signing it. Send owner, token, spender and amount, or the unsigned approve, setApprovalForAll or Permit2 calldata. Returns allow, warn, block or unknown with the allowance already on chain, the requested scope and the rule behind it, whether this raises or lowers exposure, and whether the spender is a contract, upgradeable or denylisted. Returns unknown rather than guessing. Not a guarantee a spender is honest.
Output
Returns a decision field (allow, warn, block, or unknown), the allowance already on chain, the requested scope, the rule that triggered the decision, a flag indicating whether this raises or lowers exposure, and spender metadata including whether it is a contract, upgradeable, or present on a denylist. Returns 'unknown' instead of guessing when data is insufficient.
Example use cases
Pre-sign DeFi protocol approval check
“I'm about to approve a DEX to spend my USDC — owner is 0xAbCd...1234, token is 0xA0b8...EB48, spender is 0xDef0...5678, amount is 1000000000. Tell me if it's safe, whether this spender is a known contract, and whether my exposure goes up.”
NFT collection setApprovalForAll safety review
“I need to setApprovalForAll on my NFT collection at 0xBC4C...cA00 for spender 0x1E0A...7f9B from my wallet 0xAbCd...1234. Is this spender safe to grant full collection access to — is it denylisted or upgradeable?”
Unsigned approve calldata validation before wallet signing
“My wallet is about to sign this raw calldata: 0x095ea7b3...deadbeef, sent from 0xAbCd...1234 to the USDC contract 0xA0b8...EB48. Can you decode it and tell me whether I should allow, warn, or block this approval?”
Technical details
Endpoint
POSThttps://allowance.schemasure.com/v1/guard/allowance?utm_source=zero.xyzWhen to prefer
Choose AllowanceGuard when an AI agent or wallet UI needs a structured, rule-backed risk verdict on a token or NFT allowance before a user signs it — especially when you need on-chain state (current allowance), contract metadata (upgradeable, denylisted), and exposure direction in a single call. Prefer this over generic contract scanners when you have structured approval parameters or raw unsigned calldata and need a binary/graded decision rather than a narrative audit.
Side effects
- Missing required fields (owner, token, spender, amount) returns a validation error
- Calldata that is not one of the 7 supported approval functions returns UNSUPPORTED and is not charged
- Declaring an expiration on a non-Permit2 approval kind returns a rejection
- Malformed Ethereum addresses (not matching 0x hex pattern) return a parse error
- Using 'all' for amount on a non-approval_for_all kind is rejected
- On-chain allowance unreadable due to RPC issues may result in an 'unknown' decision
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| approval | object | The grant you are about to make, described directly. |
| calldata | object | The unsigned call you are about to sign. Decodes 7 approval functions. |
Tags
x402
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