ERC-20 approval decoder: worked examples

Call Lens decodes supported token-call shapes locally and compares the recipient, spender and atomic amount with your expectations. It distinguishes ERC-20 allowances from ERC-721 token IDs using the declared standard. It never connects a wallet or evaluates contract safety.

Three fictional scenarios, calculated by the same engine as the tool. They illustrate behavior and failure cases, not customer outcomes or measured provider performance.

Unlimited ERC-20 approval

Compare maximum uint256 allowance with an entered limit.

Declared method: approve(address,uint256)
Policy flags: 2
Security verdict: Not assessed

Decoded request
Field	Value
Network	eip155:8453
Contract	0x2222222222222222222222222222222222222222
Action	Set spender allowance
Recipient / spender	0x1111111111111111111111111111111111111111
Atomic amount / bool	115792089237316195423570985008687907853269984665640564039457584007913129639935
Native atomic value	0

Run this scenario Input JSON Calculated report

Inspect every input

{
  "network": "eip155:8453",
  "tokenStandard": "ERC-20",
  "to": "0x2222222222222222222222222222222222222222",
  "data": "0x095ea7b30000000000000000000000001111111111111111111111111111111111111111ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
  "nativeValueAtomic": "0",
  "expectedRecipient": "0x1111111111111111111111111111111111111111",
  "maxAtomicAmount": "1000000"
}

A bounded approval

Use an explicit allowance while retaining the unassessed safety state.

Declared method: approve(address,uint256)
Policy flags: 0
Security verdict: Not assessed

Decoded request
Field	Value
Network	eip155:8453
Contract	0x2222222222222222222222222222222222222222
Action	Set spender allowance
Recipient / spender	0x1111111111111111111111111111111111111111
Atomic amount / bool	500000
Native atomic value	0

Run this scenario Input JSON Calculated report

Inspect every input

{
  "network": "eip155:8453",
  "tokenStandard": "ERC-20",
  "to": "0x2222222222222222222222222222222222222222",
  "data": "0x095ea7b30000000000000000000000001111111111111111111111111111111111111111000000000000000000000000000000000000000000000000000000000007a120",
  "nativeValueAtomic": "0",
  "expectedRecipient": "0x1111111111111111111111111111111111111111",
  "maxAtomicAmount": "1000000"
}

The same selector, an NFT

Interpret the integer as token ID 42 under declared ERC-721.

Declared method: approve(address,uint256)
Policy flags: 0
Security verdict: Not assessed

Decoded request
Field	Value
Network	eip155:8453
Contract	0x2222222222222222222222222222222222222222
Action	Approve this token ID (not a fungible-token allowance)
Recipient / spender	0x1111111111111111111111111111111111111111
Atomic amount / bool	42
Native atomic value	0

Run this scenario Input JSON Calculated report

Inspect every input

{
  "network": "eip155:8453",
  "tokenStandard": "ERC-721",
  "to": "0x2222222222222222222222222222222222222222",
  "data": "0x095ea7b30000000000000000000000001111111111111111111111111111111111111111000000000000000000000000000000000000000000000000000000000000002a",
  "nativeValueAtomic": "0",
  "expectedRecipient": "0x1111111111111111111111111111111111111111",
  "maxAtomicAmount": "1000000"
}

A mistake worth catching

A correctly decoded call can still target a malicious contract. No flags means only that the supplied checks found no mismatch, not that signing is safe.

Use the method with your records

Decode only exact two-word transfer, approve and setApprovalForAll ABI shapes. Compare supplied recipient/spender and limit; identify broad approval and attached native value.

No chain simulation, malicious-contract detection, token identity lookup, balance inspection or safety verdict.

Read the complete method, sources and input contract. Updated 2026-09-19; by the AGI Scorecard team.

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