# ERC-721 Token Owner Lookup

> ERC-721 Token Owner Lookup is a paid API for AI agents from biosfera.46-62-215-147.sslip.io, paid per call via x402, $0.0015/call, status unknown (last checked 2026-10-01).

Returns the current owner address of a specific ERC-721 NFT token ID, along with the collection's name and symbol, across Base, Ethereum, Arbitrum, Optimism, and Polygon.

## Facts

- Endpoint: GET https://biosfera.46-62-215-147.sslip.io/o/erc721-owner?utm_source=zero.xyz
- Price: $0.0015/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-721-token-owner-lookup-1de5fd25
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8Y6BSDfDRQOWWcPKat7OU

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-721-token-owner-lookup-1de5fd25
```

Example prompt: Who owns token ID 1234 of the NFT contract 0xBC4CA0EdA7647A8aB7C2061c2E118A18a936f13D on Ethereum?

## When to prefer this

Use this endpoint when you need to look up the current owner of a specific ERC-721 NFT token on Base, Ethereum, Arbitrum, Optimism, or Polygon. It is the right choice for ownership verification, NFT-gating, provenance research, or post-transfer confirmation. Prefer this over general blockchain explorers when you need a structured, machine-readable response with collection metadata (name and symbol) included.

## Known failure modes

- Token ID does not exist or has no owner — returns exists=false
- Invalid contract address format — rejected by schema validation
- Contract is not a valid ERC-721 contract — may return an error or unexpected response
- Unsupported chain requested — rejected by enum validation
- Token ID out of range or malformed — rejected by pattern validation
- Network RPC timeout or congestion — may result in a delayed or failed response

## How this service works

Use when you need the current owner of an ERC-721 token id on Base, Ethereum, Arbitrum, Optimism or Polygon via ownerOf, plus the collection's name and symbol. Returns exists=false if the id has no owner.

## Output

Returns the owner's wallet address (a 0x Ethereum address), the collection's name, the collection's symbol, and an exists boolean. If the token ID has no owner (unminted or burned), exists is false and no owner address is returned.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "chain",
      "contract",
      "token_id"
     ],
     "properties": {
      "chain": {
       "enum": [
        "base",
        "ethereum",
        "arbitrum",
        "optimism",
        "polygon"
       ],
       "type": "string"
      },
      "contract": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$"
      },
      "token_id": {
       "type": "string",
       "pattern": "^[0-9]{1,78}$"
      }
     },
     "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-721-token-owner-lookup-1de5fd25/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)