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ERC-20 Approve Calldata Builder with Unlimited Allowance Flagging
x402
ERC-20 Approve Calldata Builder with Unlimited Allowance Flagging is a paid API for AI agents from evm-canon-base.onrender.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).
Encodes ERC-20 approve() calldata for a given spender and amount, automatically flagging unlimited (max uint256) allowances before any transaction is signed
Price / call$0.01
Success—
StatusUnknown
How this service works
Build ERC-20 approval calldata, flagging unlimited allowances before anything is signed
Output
Returns ABI-encoded hex calldata for the ERC-20 approve(address,uint256) function, along with a risk flag indicating whether the allowance is unlimited (max uint256). The agent can pass this calldata directly into a transaction without further encoding. No transaction is submitted; the endpoint is purely a calldata builder.
Example use cases
DeFi swap pre-approval encoding
“I need to approve Uniswap V3's swap router (0xE592427A0AEce92De3Edee1F18E0157C05861564) to spend 500 DAI (0x6B175474E89094C44Da98b954EedeAC495271d0F, 18 decimals) on my behalf — give me the calldata and tell me if it triggers an unlimited-allowance warning.”
Unlimited allowance risk check
“Encode an ERC-20 approve for the maximum possible amount (unlimited) for spender 0xabc123... on WETH (0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2, 18 decimals), and make sure the response flags that this is an unlimited allowance before I sign anything.”
Safe allowance for lending protocol
“Build the approve() calldata to allow Aave's lending pool (0x7d2768dE32b0b80b7a3454c06BdAc94A69DDc7A9) to spend exactly 2500 USDC (0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48, 6 decimals) — I want to confirm it won't be flagged as unlimited.”
Technical details
Endpoint
POSThttps://evm-canon-base.onrender.com/encode/approveWhen to prefer
Choose this endpoint when you need ERC-20 approve() calldata with a built-in safety check for unlimited allowances before any signing occurs. It is ideal for DeFi agents that must encode approvals deterministically while surfacing risk signals to users. Prefer it over raw ABI encoding when the unlimited-allowance flag matters for user consent flows, or when you want a single canonical calldata builder without setting up a local ABI library.
Side effects
- Invalid or checksummed token address format returns a 400 error
- Invalid spender address returns a 400 error
- Amount exceeding uint256 max returns a validation error
- Unsupported token or unresolvable decimals may return an error
- Network timeout on the render.com host (cold start latency)
- Payment failure (x402) if USDC balance is insufficient
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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