# ERC-20 Token Allowance Lookup

> ERC-20 Token Allowance Lookup is a paid API for AI agents from biosfera.46-62-215-147.sslip.io, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-01).

Returns the amount of an ERC-20 token a spender is approved to transfer on behalf of an owner, in both raw units and decimal value, across major EVM chains.

## Facts

- Endpoint: GET https://biosfera.46-62-215-147.sslip.io/o/erc20-allowance?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-20-token-allowance-lookup-ffc86172
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zcVpqk1zSmTNmk9e8Pf57

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-ffc86172
```

Example prompt: What's the USDC allowance that the Uniswap v3 router (0xE592427A0AEce92De3Edee1F18E0157C05861564) has to spend from my wallet (0xAbCd...1234) on Ethereum?

## When to prefer this

Use this endpoint when you need to check on-chain ERC-20 token approvals across Base, Ethereum, Arbitrum, Optimism, or Polygon without running your own RPC node. It's ideal for DeFi agents that need to verify spending permissions before executing swaps, transfers, or vault interactions, or for monitoring and auditing token approvals granted to third-party contracts.

## Known failure modes

- Invalid Ethereum address format for owner, spender, or token returns a 400 error
- Unsupported chain name returns a validation error
- Token address that is not a valid ERC-20 contract may return zero or a contract call error
- RPC node timeout or chain congestion may cause slow or failed responses
- Zero allowance returned when spender has not been approved — not an error, but may be misread as a failure

## How this service works

Use when you need how much of an ERC-20 token a spender is approved to move from an owner, on Base, Ethereum, Arbitrum, Optimism or Polygon, via allowance(owner, spender). Returns raw units and decimal value.

## Output

Returns the approved allowance amount in raw token units (e.g. wei-equivalent integers) and as a human-readable decimal value adjusted for the token's decimals, along with metadata such as token symbol and decimal precision.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "chain",
      "token",
      "owner",
      "spender"
     ],
     "properties": {
      "chain": {
       "enum": [
        "base",
        "ethereum",
        "arbitrum",
        "optimism",
        "polygon"
       ],
       "type": "string"
      },
      "owner": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$"
      },
      "token": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$"
      },
      "spender": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$"
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-token-allowance-lookup-ffc86172/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from biosfera.46-62-215-147.sslip.io](https://www.zero.xyz/host/biosfera.46-62-215-147.sslip.io/llms.txt)