Guard Allowance

{
  "confidence": 1,
  "data_versions": {
    "abi_packs": "2026-08-03.1",
    "allowance_sentinels": "4",
    "chain": "eip155:8453",
    "denylist": "2026-08-03.1",
    "policy": "2026-09-19",
    "signature_index": "2026-08-03.1"
  },
  "evidence": [
    {
      "code": "CURRENT_ALLOWANCE_UNREADABLE",
      "detail": "The allowance 0x2626664c2603336E57B271c5C0b26F421741e481 already holds could not be read: no RPC endpoint is configured, so the allowance this spender already holds could not be read. Whether this request adds to an existing allowance or replaces one is therefore unknown. It does not change the answer: this request cannot increase what the spender can move.",
      "severity": "info",
      "source": "rpc"
    },
    {
      "code": "SPENDER_CODE_UNREADABLE",
      "detail": "Whether 0x2626664c2603336E57B271c5C0b26F421741e481 is a contract or an account could not be determined: no RPC endpoint is configured, so it is unknown whether the spender has code. It does not change the answer: this request cannot increase what the spender can move.",
      "severity": "info",
      "source": "rpc"
    },
    {
      "code": "SPENDER_PROXY_OPAQUE",
      "detail": "The code that would execute on 0x2626664c2603336E57B271c5C0b26F421741e481's behalf could not be resolved: no RPC endpoint is configured, so no slot could be read. An allowance to a contract whose executing code is unknown is an allowance to unknown code. It does not change the answer: this request cannot increase what the spender can move.",
      "severity": "info",
      "source": "rpc"
    }
  ],
  "ok": true,
  "policy_version": "2026-09-19",
  "request_hash": "sha256:a88cb1eea90d411505068349493a5cf35a1f2b46f4cbb4185330ffd4094c65fb",
  "result": {
    "chain": "eip155:8453",
    "classification": {
      "basis": "the allowance is zero, which is bounded without reference to the token's supply",
      "resulting_allowance": "0",
      "scope": "bounded",
      "subject": "resulting_allowance",
      "supply_checked": true,
      "total_supply": null
    },
    "current": {
      "amount": null,
      "detail": "no RPC endpoint is configured, so the allowance this spender already holds could not be read",
      "expiration": null,
      "source": "unreadable"
    },
    "decode": {
      "candidates": [],
      "selector": "0x095ea7b3",
      "signature": "approve(address,uint256)",
      "source": "bundled-abi"
    },
    "delta": {
      "detail": "this sets the allowance to zero, which cannot increase exposure whatever it is now; the value being replaced could not be read, so whether it is a reduction or already zero is unknown",
      "difference": null,
      "direction": "unknown",
      "increases_exposure": false
    },
    "denylist_hits": [],
    "input_shape": "calldata",
    "request": {
      "amount": "0",
      "deadline": null,
      "expiration": null,
      "kind": "erc20_approve",
      "mode": "absolute",
      "owner": "0x9f2C5E4a8DB1C3A7e6b0d4f8C1e2A5b7d9c0E3f4",
      "spender": "0x2626664c2603336E57B271c5C0b26F421741e481",
      "summary": "Revoke 0x2626664c2603336E57B271c5C0b26F421741e481's allowance on token 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 by setting it to zero.",
      "target": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "token_id": null
    },
    "rpc": {
      "configured": false,
      "endpoints": [],
      "reachable": null
    },
    "spender": {
      "address": "0x2626664c2603336E57B271c5C0b26F421741e481",
      "detail": "no RPC endpoint is configured, so it is unknown whether the spender has code",
      "is_contract": null,
      "proxy": {
        "address": "0x2626664c2603336E57B271c5C0b26F421741e481",
        "admin": null,
        "beacon": null,
        "detail": "no RPC endpoint is configured, so no slot could be read",
        "implementation": null,
        "kind": "unknown",
        "slots_probed": [],
        "upgradeable": null
      }
    },
    "token": {
      "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "code_size": null,
      "decimals": null,
      "detail": "no RPC configured, so code presence could not be read; no RPC configured, so token metadata could not be read",
      "has_code": null,
      "is_erc721": null,
      "symbol": null,
      "total_supply": null
    }
  },
  "risk_codes": [],
  "verdict": "allow",
  "warnings": []
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://allowance.schemasure.com/v1/guard/allowance' \
  -H 'content-type: application/json' \
  --data-raw '{"calldata":{"data":"0x095ea7b30000000000000000000000002626664c2603336e57b271c5c0b26f421741e4810000000000000000000000000000000000000000000000000000000000000000","from":"0x9F2C5E4A8db1C3a7E6B0d4f8C1E2a5b7D9C0e3F4","to":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://allowance.schemasure.com/v1/guard/allowance' \
  -H 'content-type: application/json' \
  --data-raw '{"calldata":{"data":"0x095ea7b30000000000000000000000002626664c2603336e57b271c5c0b26f421741e4810000000000000000000000000000000000000000000000000000000000000000","from":"0x9F2C5E4A8db1C3a7E6B0d4f8C1E2a5b7D9C0e3F4","to":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.03 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.03" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.03 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fallowance.schemasure.com%2Fv1%2Fguard%2Fallowance&method=POST
const res = await pay("https://allowance.schemasure.com/v1/guard/allowance", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "calldata": {
      "data": "0x095ea7b30000000000000000000000002626664c2603336e57b271c5c0b26f421741e4810000000000000000000000000000000000000000000000000000000000000000",
      "from": "0x9F2C5E4A8db1C3a7E6B0d4f8C1E2a5b7D9C0e3F4",
      "to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
    }
  }),
});
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.03 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.03"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://allowance.schemasure.com/v1/guard/allowance",
        json={
            "calldata": {
                "data": "0x095ea7b30000000000000000000000002626664c2603336e57b271c5c0b26f421741e4810000000000000000000000000000000000000000000000000000000000000000",
                "from": "0x9F2C5E4A8db1C3a7E6B0d4f8C1E2a5b7D9C0e3F4",
                "to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
            },
        },
    )
    print(res.status_code, res.text)