{"id":"ae68a5be-a173-499b-bd52-8ba4f1811cca","shortId":"sU25bD","kind":"x402","title":"Query NFT ownership data via x402 micropayment on Base for $0.02 per request.","tagline":"Query NFT ownership data via x402 micropayment on Base for $0.02 per request.","description":"This endpoint at lowpaymentfee.com returns the owner of NFT #21 via a pay-per-call x402 protocol. The endpoint accepts POST requests and is settled in USDC on the Base network. The x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (6 decimals), which equals $0.02 per request. No API keys, rate limits, or subscriptions are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe broader lowpaymentfee.com platform offers a suite of x402-gated APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/Web3 data (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are listed at $0.02 per request and settle on Base via USDC.\n\nThis specific endpoint (/api/v1/nfts/21/owner) is narrowly scoped to returning ownership information for a single NFT (ID 21). The response MIME type is application/json. No OpenAPI schema, request body schema, or response body schema is published, so the exact request and response formats must be inferred or discovered by calling the endpoint.","tags":[],"capabilities":["nft-ownership-lookup","x402-micropayment","usdc-settlement","base-network","pay-per-request","no-api-key"],"categories":["web3","nft"],"synonyms":["NFT owner lookup","NFT ownership API","x402 NFT endpoint","Base USDC micropayment API","on-chain NFT data","token owner query"],"warnings":["No OpenAPI or request/response schema is published — callers must discover the expected body format by trial.","This endpoint is hardcoded to NFT ID 21; it is unclear whether other NFT IDs are available at different paths.","Documentation pages (/api, /pricing, /README) returned no useful content beyond 'Connect wallet'.","The nature and source of the NFT data (which collection, which chain for the NFT itself) is not documented."],"endpointUrl":"https://lowpaymentfee.com/api/v1/nfts/21/owner","protocol":"x402","transport":"http","auth":{"type":"x402","details":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","scheme":"exact","network":"base","mimeType":"application/json","resource":"https://lowpaymentfee.com/api/v1/nfts/21/owner","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live (402 challenge captured) and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI schema, no documented request/response format, no examples, and the endpoint is narrowly scoped to a single NFT ID. The crawled pages beyond the homepage returned only 'Connect wallet' with no additional 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'0.02':11,24,76,146 '000':67 '20':66 '21':36,171 '6':72 'Base USDC micropayment API' 'NFT owner lookup' 'NFT ownership API' 'accept':47 'advertis':62 'ai/ml':117 'analysi':120 'analyt':116 'api':80,113 'application/json':177 'attach':90 'base':9,22,57,68,152 'base-network' 'bodi':182,186 'broader':103 'call':42,203 'caller':88 'challeng':61 'classif':122 'convers':139 'data':4,17,115,125 'decim':73 'discov':201 'embed':123 'endpoint':28,46,142,157,205 'equal':75 'estim':133 'exact':192 'exchang':128 'feed':127 'finance/web3':124 'format':196 'gas':132 'gate':112 'generat':140 'geocod':137 'header':95 'id':170 'infer':118,199 'inform':165 'infrastructur':135 'key':81 'limit':83 'list':144 'lowpaymentfee.com':30,104 'maxamountrequir':64 'micropay':7,20 'mime':174 'must':197 'narrowli':160 'network':58 'nft':2,15,35,169 'nft-ownership-lookup' 'no-api-key' 'offer':106 'on-chain NFT data' 'openapi':179 'owner':33 'ownership':3,16,164 'pay':40 'pay-per-cal':39 'pay-per-request' 'payment':94,100 'per':12,25,41,77,147 'platform':105 'post':48 'price':126 'proof':101 'protocol':44 'publish':189 'queri':1,14 'quot':131 'rate':82,129 'request':13,26,49,78,148,181,193 'requir':87 'respons':173,185,195 'return':31,163 'schema':180,183,187 'scope':161 'sentiment':119 'settl':52,150 'simpli':89 'singl':168 'span':114 'specif':156 'subscript':85 'suit':108 'summar':121 'token':130 'token owner query' 'type':175 'unit':69 'usdc':54,71,154 'usdc-settlement' 'util':136 'valid':98,138 'via':5,18,37,153 'x':93 'x-payment':92 'x402':6,19,43,60,99,111 'x402 NFT endpoint' 'x402-gated':110 'x402-micropayment'","prices":[{"id":"1f3bd02f-790e-48fe-ba20-b8ec8eaaf0c1","listingId":"ae68a5be-a173-499b-bd52-8ba4f1811cca","amountUsd":null,"unit":"per_call","nativeCurrency":"USD COIN","nativeAmount":"20000","chain":"base","payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","paymentMethod":"x402-usd coin","isPrimary":true,"details":{"scheme":"exact","mime_type":"application/json","accepts_all":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","scheme":"exact","network":"base","mimeType":"application/json","resource":"https://lowpaymentfee.com/api/v1/nfts/21/owner","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:27.761Z"}],"sources":[{"listingId":"ae68a5be-a173-499b-bd52-8ba4f1811cca","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/nfts/21/owner","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:27.761Z","lastSeenAt":"2026-04-22T19:33:08.626Z"}],"details":{"listingId":"ae68a5be-a173-499b-bd52-8ba4f1811cca","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/nfts/21/owner \\\n  -H \"X-PAYMENT: <x402_payment_proof>\" \\\n  -H \"Content-Type: application/json\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The x402 challenge advertises maxAmountRequired of 20000 base units of USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/nfts/21/owner"},{"claim":"All endpoints on lowpaymentfee.com are listed at $0.02 per request with no API keys, no rate limits, and instant access on Base","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/nfts/21/owner"}],"useCases":["Querying the current owner of a specific NFT programmatically","Integrating NFT ownership checks into agent workflows without API key management","Verifying NFT provenance or ownership as part of a Web3 application"],"bestFor":["Agents needing one-off NFT ownership lookups with no subscription overhead","Developers prototyping Web3 apps that need pay-per-call NFT data","x402-compatible wallets and agents on the Base network"],"notFor":["Bulk or batch NFT ownership queries across many token IDs (only NFT #21 is served by this endpoint)","Users who need free or pre-paid API access without crypto wallet integration","Querying NFTs on networks other than Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:12:58.95Z"},"updatedAt":"2026-04-22T19:33:08.626Z"}}