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ERC-721 NFT Balance Checker
x402
ERC-721 NFT Balance Checker is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-29).
Returns how many NFTs from a specific ERC-721 collection a given wallet address holds on a specified EVM-compatible chain
Price / call$0.003
Success—
StatusUnknown
How this service works
How many NFTs from one collection an address holds — Genesis402 / UnyKorn Operator Network
Output
Returns a JSON object with ok status, the type field 'erc721-balance', and a payment receipt including the transaction hash, amount paid in USD, and a unique receipt ID. The NFT balance count for the specified owner and contract is included in the response payload.
Example use cases
NFT portfolio snapshot for a wallet
“Can you check how many NFTs wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 holds from the Bored Ape Yacht Club contract 0xBC4CA0EdA7647A8aB7C2061c2E118A18a936f13D on Ethereum?”
Verify NFT gate eligibility on Base
“I need to confirm whether wallet 0xAbCd1234AbCd1234AbCd1234AbCd1234AbCd1234 owns any NFTs from our membership collection at 0x1234567890abcdef1234567890abcdef12345678 on Base — can you check their balance?”
Monitor whale NFT holdings on Polygon
“How many NFTs from the collection at 0xA1B2C3D4A1B2C3D4A1B2C3D4A1B2C3D4A1B2C3D4 does the whale wallet 0xF1F2F3F4F5F6F7F8F9F0F1F2F3F4F5F6F7F8F9F0 currently hold on Polygon?”
Technical details
Endpoint
POSThttps://twin.unykorn.org/erc721-balance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to programmatically check how many NFTs a specific wallet holds from a particular ERC-721 collection on any of the supported EVM chains (Ethereum, Base, Polygon, Arbitrum, Optimism, BSC, Avalanche, Gnosis, Linea, Scroll). It is ideal for NFT-gating logic, wallet analysis, ownership verification, and portfolio queries where a precise balance count per collection is needed rather than a list of token IDs.
Side effects
- Invalid wallet address format (not a valid 0x hex address) returns validation error
- Invalid contract address format returns validation error
- Unsupported chain name returns enum validation error
- Contract address is not an ERC-721 contract may return zero or error
- Network timeout or RPC failure may return non-ok response
- Payment failure via x402 protocol prevents the query from executing
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| params | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"type": "erc721-balance",
"receipt": {
"tx_hash": "0x<64hex>",
"amount_usd": 0.25,
"receipt_id": "g402-<16hex>"
},
"generated_at": "<iso8601>"
}
}Tags
x402
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