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ERC-721 Token ID by Owner Index
x402
ERC-721 Token ID by Owner Index is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-01).
Returns the Nth token ID owned by a specific address in an ERC-721 NFT collection on a given EVM chain
Price / call$0.003
Success—
StatusUnknown
How this service works
The Nth token id an address owns in a collection — Genesis402 / UnyKorn Operator Network
Output
Returns a JSON object with ok=true, type='erc721-token-of-owner', the resolved token ID for the given index, and a payment receipt including transaction hash, amount in USD, and a unique receipt ID.
Example use cases
Inventory first NFT in a collection
“What is the token ID of the very first NFT (index 0) that the wallet 0xDead...Beef owns in the ERC-721 contract 0xCafe...1234 on Ethereum?”
Portfolio enumeration for airdrop eligibility
“I need to find the third NFT (index 2) held by address 0xAaaa...Bbbb in the Polygon NFT contract 0x9999...FFFF — can you get that token ID?”
Cross-chain NFT holder verification
“Tell me the token ID at index 1 for owner 0x1111...2222 in the NFT collection at 0x3333...4444 on Arbitrum.”
Technical details
Endpoint
POSThttps://twin.unykorn.org/erc721-token-of-owner?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to enumerate or iterate through the specific token IDs that a wallet address owns in an ERC-721 collection by positional index. It complements the 'NFT balance' endpoint (which gives the count) — call the balance endpoint first to know the range, then use this endpoint to retrieve each token ID. Ideal for building full NFT inventory lists, verifying ownership of a specific token, or feeding token IDs into downstream metadata lookups.
Side effects
- Index out of bounds — owner holds fewer NFTs than the requested index
- Invalid wallet address format (non-0x or wrong length)
- Invalid contract address format
- Unsupported chain value outside the accepted enum
- Contract is not a valid ERC-721 contract
- Network or RPC timeout for the specified chain
- Payment failure via x402 protocol
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| params | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"type": "erc721-token-of-owner",
"receipt": {
"tx_hash": "0x<64hex>",
"amount_usd": 0.25,
"receipt_id": "g402-<16hex>"
},
"generated_at": "<iso8601>"
}
}Tags
x402
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