{"uid":"cap_i3ljwkDEF4AgyUKSiVqod","slug":"erc-721-token-id-by-owner-index-eaa518bb","name":"ERC-721 Token ID by Owner Index","description":"The Nth token id an address owns in a collection — Genesis402 / UnyKorn Operator Network","url":"https://twin.unykorn.org/erc721-token-of-owner?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"},"index":{"type":"integer","minimum":0},"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-token-of-owner","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_miFuc-x9aJqyOz6mW_qzi","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 the Nth token ID owned by a specific address in an ERC-721 NFT collection on a given EVM chain","exampleAgentPrompt":"What's the token ID of the 2nd NFT that wallet 0xAbCd...1234 owns in the collection at contract 0x1234...abcd on Base?","exampleUseCases":[{"title":"Inventory first NFT in a collection","prompt":"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?"},{"title":"Portfolio enumeration for airdrop eligibility","prompt":"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?"},{"title":"Cross-chain NFT holder verification","prompt":"Tell me the token ID at index 1 for owner 0x1111...2222 in the NFT collection at 0x3333...4444 on Arbitrum."}],"resultDescription":"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.","failureModes":["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"],"whenToPreferThis":"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.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T18:55:34.488Z","isFirstParty":false,"canonicalSlug":"erc-721-token-id-by-owner-index-eaa518bb"}