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Agent402 ERC-721 Owner Lookup
x402
Agent402 ERC-721 Owner Lookup is a paid API for AI agents from agent402.tools, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).
Returns the current owner address of a specific ERC-721 NFT token given a contract address and token ID, across multiple EVM-compatible networks.
Price / call$0.002
Success—
StatusUnknown
How this service works
Who owns this NFT? Calls ownerOf(tokenId) on any ERC-721 contract on Ethereum, Base, Polygon, Arbitrum, or Optimism. Complements nft-holdings (which lists a WALLET's NFTs) - this answers by TOKEN. Keyless multi-endpoint failover. ?contract=0x…&tokenId=123&network=ethereum
Output
Returns a JSON object containing the owner wallet address (0x…), the blockchain network queried, the token ID (normalized), and the contract address. This allows the agent to definitively identify the current on-chain holder of a specific NFT.
Example use cases
NFT provenance verification
“Can you check who currently owns token ID 1234 of the NFT contract 0xBC4CA0EdA7647A8aB7C2061c2E118A18a936f13D on Ethereum? I need to verify the current holder before making an offer.”
Cross-chain NFT ownership audit
“Find out who holds token 42 of contract 0x8a90CAb2b38dba80c64b7734e58Ee1dB38B8992e on Base — I'm building a dashboard that tracks ownership across chains.”
NFT gating access check
“Look up the owner of token ID 0xaf2c on the ERC-721 contract 0x57f1887a8BF19b14fC0dF6Fd9B2acc9Af147eA85 on Polygon so I can verify if a user is eligible for gated content.”
Technical details
Endpoint
GEThttps://agent402.tools/api/erc721-ownerWhen to prefer
Use this endpoint when you need a lightweight, pay-per-call NFT owner lookup without signing up for an API key or managing an RPC provider. It covers multiple EVM networks (Ethereum, Base, Polygon, Arbitrum, Optimism) in a single interface and is ideal for agents that need on-demand ownership verification as part of a larger workflow, especially within an x402 payment-enabled pipeline.
Side effects
- Invalid contract address (not a valid ERC-721 contract) returns an error
- Token ID does not exist on the specified contract
- Unsupported network name returns an error
- Contract address is not checksummed or malformed
- Network RPC unavailable causing a timeout
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"owner": "0x…",
"network": "ethereum",
"tokenId": "0xaf2c…",
"contract": "0x57f1…"
}
}Tags
x402
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