{"id":"b3e16acd-0cd9-4ea1-906f-7ba29694e160","shortId":"KzwTFQ","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 NFT ownership information for a specific NFT (ID 9) 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 provider, lowpaymentfee.com, hosts a broader catalog of x402-gated APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities, all priced uniformly at $0.02 per request on Base. This specific endpoint (/api/v1/nfts/9/owner) appears to serve NFT owner lookup, though no detailed documentation or response schema was found in the crawl. The response MIME type is application/json.\n\nBecause no OpenAPI spec, request/response examples, or detailed documentation were discovered, the exact request body format and response structure are unknown. Callers should expect a JSON response containing owner address information for the queried NFT, but the precise fields are unconfirmed.","tags":[],"capabilities":["nft-ownership-lookup","x402-micropayment","usdc-settlement","base-network","pay-per-call","no-api-key","json-response"],"categories":["web3","nft"],"synonyms":["NFT owner lookup","NFT ownership API","who owns NFT","token holder query","x402 NFT API","Base USDC micropayment API"],"warnings":["No OpenAPI spec or detailed documentation found for this endpoint.","Request body format and response schema are unknown — no examples available.","The endpoint path is hardcoded to NFT ID 9; it is unclear whether other NFT IDs are supported via similar paths.","The broader lowpaymentfee.com catalog lists many endpoints but none had accessible documentation pages (all returned 'Connect wallet' only)."],"endpointUrl":"https://lowpaymentfee.com/api/v1/nfts/9/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/9/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), but there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page listing, and the specific functionality (NFT owner lookup for ID 9) is narrow and undocumented. Effectively a stub 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'0.02':11,24,80,132 '000':71 '20':70 '6':76 '9':40 'Base USDC micropayment API' 'NFT owner lookup' 'NFT ownership API' 'accept':51 'address':194 'advertis':66 'ai/ml':121 'analyt':120 'api':84,117 'appear':141 'application/json':164 'attach':94 'base':9,22,61,72,136 'base-network' 'bodi':179 'broader':111 'call':46 'caller':92,186 'catalog':112 'challeng':65 'contain':192 'crawl':158 'data':4,17,119,124 'decim':77 'detail':149,172 'discov':175 'document':150,173 'endpoint':28,50,139 'equal':79 'exact':177 'exampl':170 'expect':188 'field':203 'finance/web3':123 'format':180 'found':155 'gate':116 'header':99 'host':109 'id':39 'infer':122 'inform':34,195 'infrastructur':126 'json':190 'json-response' 'key':85 'limit':87 'lookup':146 'lowpaymentfee.com':30,108 'maxamountrequir':68 'micropay':7,20 'mime':161 'network':62 'nft':2,15,32,38,144,199 'nft-ownership-lookup' 'no-api-key' 'openapi':167 'owner':145,193 'ownership':3,16,33 'pay':44 'pay-per-cal':43 'pay-per-call' 'payment':98,104 'per':12,25,45,81,133 'post':52 'precis':202 'price':129 'proof':105 'protocol':48 'provid':107 'queri':1,14,198 'rate':86 'request':13,26,53,82,134,178 'request/response':169 'requir':91 'respons':152,160,182,191 'return':31 'schema':153 'serv':143 'settl':56 'simpli':93 'span':118 'spec':168 'specif':37,138 'structur':183 'subscript':89 'though':147 'token holder query' 'type':162 'unconfirm':205 'uniform':130 'unit':73 'unknown':185 'usdc':58,75 'usdc-settlement' 'util':127 'valid':102 'via':5,18,41 'who owns NFT' 'x':97 'x-payment':96 'x402':6,19,47,64,103,115 'x402 NFT API' 'x402-gated':114 'x402-micropayment'","prices":[{"id":"e151c949-d86c-4eb1-9154-e94a6a8dad47","listingId":"b3e16acd-0cd9-4ea1-906f-7ba29694e160","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/9/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":"2026-04-21T18:32:28.818Z"}],"sources":[{"listingId":"b3e16acd-0cd9-4ea1-906f-7ba29694e160","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/nfts/9/owner","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:28.818Z","lastSeenAt":"2026-04-22T12:05:29.672Z"}],"details":{"listingId":"b3e16acd-0cd9-4ea1-906f-7ba29694e160","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/nfts/9/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 endpoint returns HTTP 402 with an x402 challenge advertising USDC on Base at 20,000 base units ($0.02).","source_url":"https://lowpaymentfee.com/api/v1/nfts/9/owner"},{"claim":"The provider advertises $0.02/request pricing with no API keys, no rate limits, and instant access on Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"The asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 is USDC on Base with 6 decimals.","source_url":"https://lowpaymentfee.com"}],"useCases":["Querying the current owner of a specific NFT programmatically","Verifying NFT ownership as part of a gating or access-control workflow","Building dashboards that display NFT holder information"],"bestFor":["Agents or apps that need on-demand NFT owner data without managing API keys","Low-volume, pay-as-you-go NFT ownership queries","Developers experimenting with x402 payment protocol integrations"],"notFor":["Bulk or high-throughput NFT indexing (no batch endpoint documented)","Querying NFTs beyond ID 9 (only this specific resource path is confirmed)","Users who cannot settle payments in USDC on Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:12:57.052Z"},"updatedAt":"2026-04-22T12:05:29.672Z"}}