{"uid":"cap_uP_zvPKzyk5BtQ6auROaD","slug":"erc-721-nft-balance-checker-566a55a8","name":"ERC-721 NFT Balance Checker","description":"How many NFTs from one collection an address holds — Genesis402 / UnyKorn Operator Network","url":"https://twin.unykorn.org/erc721-balance?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"params":{"type":"object","properties":{"chain":{"enum":["ethereum","base","polygon","arbitrum","optimism","bsc","avalanche","gnosis","linea","scroll"],"type":"string"},"owner":{"type":"string","pattern":"^0x[0-9a-fA-F]{40}$"},"contract":{"type":"string","pattern":"^0x[0-9a-fA-F]{40}$"}}}}},"responseSchema":{"type":"json","example":{"ok":true,"type":"erc721-balance","receipt":{"tx_hash":"0x<64hex>","amount_usd":0.003,"receipt_id":"g402-<16hex>"},"generated_at":"<iso8601>"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.003","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.003/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.003","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.003","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_l_71AEeJVjWICDKi2imVc","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.003","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Returns how many NFTs from a specific ERC-721 collection a given wallet address holds on a specified EVM-compatible chain","exampleAgentPrompt":"How many NFTs from the collection at contract 0xBC4CA0EdA7647A8aB7C2061c2E118A18a936f13D does wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 hold on Ethereum?","exampleUseCases":[{"title":"NFT portfolio snapshot for a wallet","prompt":"Can you check how many NFTs wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 holds from the Bored Ape Yacht Club contract 0xBC4CA0EdA7647A8aB7C2061c2E118A18a936f13D on Ethereum?"},{"title":"Verify NFT gate eligibility on Base","prompt":"I need to confirm whether wallet 0xAbCd1234AbCd1234AbCd1234AbCd1234AbCd1234 owns any NFTs from our membership collection at 0x1234567890abcdef1234567890abcdef12345678 on Base — can you check their balance?"},{"title":"Monitor whale NFT holdings on Polygon","prompt":"How many NFTs from the collection at 0xA1B2C3D4A1B2C3D4A1B2C3D4A1B2C3D4A1B2C3D4 does the whale wallet 0xF1F2F3F4F5F6F7F8F9F0F1F2F3F4F5F6F7F8F9F0 currently hold on Polygon?"}],"resultDescription":"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.","failureModes":["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"],"whenToPreferThis":"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.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T18:55:19.263Z","isFirstParty":false,"canonicalSlug":"erc-721-nft-balance-checker-566a55a8"}