# ERC-20 Token Allowance Lookup (Ethereum)

> ERC-20 Token Allowance Lookup (Ethereum) is a paid API for AI agents from saylorinnovations.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-03).

Returns the current ERC-20 token allowance granted by a token owner to a spender on Ethereum mainnet

## Facts

- Endpoint: GET https://saylorinnovations.com/api/evm/ethereum/allowance/:address/:address2/:address3?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-03
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-20-token-allowance-lookup-ethereum-8771991d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1G24uUnK-XjrldotWrMF-

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability erc-20-token-allowance-lookup-ethereum-8771991d
```

Example prompt: Check the ERC-20 token allowance on Ethereum for owner address 0xAbc...123 and spender address 0xDef...456 on token contract 0x789...GHI — I want to know how many tokens the spender is approved to transfer.

## When to prefer this

Use this endpoint when you need to programmatically check ERC-20 spending allowances on Ethereum mainnet without running your own node or integrating a full blockchain SDK. Ideal for DeFi agents monitoring approvals, security tools auditing wallet permissions, or dApp workflows that need to verify allowances before initiating transfers.

## Known failure modes

- Invalid Ethereum address format for any of the three address parameters returns an error
- Token contract address is not a valid ERC-20 contract (no allowance function) causes call failure
- Network congestion or RPC issues may cause timeouts
- Zero allowance returned when no approval has been set (valid response, not an error)
- Wrong address ordering (owner vs spender swapped) returns a valid but incorrect result silently

## How this service works

ERC-20 Allowance (ethereum). Ethereum ERC-20 allowance: how much a spender may move from an owner, human-readable, with an unlimited-approval flag.

## Output

Returns the on-chain ERC-20 allowance value — the number of tokens (typically in the token's smallest unit) that the spender is permitted to transfer on behalf of the owner for the specified token contract on Ethereum mainnet.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-token-allowance-lookup-ethereum-8771991d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from saylorinnovations.com](https://www.zero.xyz/host/saylorinnovations.com/llms.txt)