{"id":"6050629f-f48b-4438-b2ba-270e432630e7","shortId":"gqtXnB","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 (token ID 99) 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 or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe provider hosts a broader suite of APIs spanning data & analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are listed at $0.02 per request on the same x402 payment model using USDC on Base. This specific endpoint (/api/v1/nfts/99/owner) is part of the Web3/NFT category, though it is not explicitly listed on the provider's landing page among the featured APIs.\n\nThe endpoint is live and returns a proper 402 challenge. However, there is no OpenAPI schema, no documentation beyond the landing page, and no example request/response payloads available. The actual response format for the NFT owner query is unknown — it likely returns JSON with owner address information, but this is inferred, not documented.","tags":[],"capabilities":["nft-ownership-query","x402-micropayment","usdc-payment","base-network","pay-per-call","no-api-key","post-endpoint"],"categories":["web3","nft"],"synonyms":["NFT owner lookup","NFT ownership API","token owner query","x402 NFT API","Base USDC micropayment API","NFT holder check"],"warnings":["No OpenAPI or schema documentation available for this endpoint","The /api/v1/nfts/99/owner path is not listed among the provider's advertised APIs on the landing page","Response format is unknown — no example responses are available","The endpoint is hardcoded to token ID 99; it is unclear if other token IDs are supported via similar paths"],"endpointUrl":"https://lowpaymentfee.com/api/v1/nfts/99/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/99/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 and returns a valid x402 402 challenge with clear pricing. However, there is no OpenAPI schema, no documented request/response format, no examples, and the specific NFT endpoint is not even listed on the provider's own landing page. The actual behavior of the endpoint is entirely 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'0.02':11,24,81,146 '000':72 '20':71 '402':193 '6':77 '99':41 'Base USDC micropayment API' 'NFT holder check' 'NFT owner lookup' 'NFT ownership API' 'accept':52 'actual':214 'address':230 'advertis':67 'ai/ml':117 'among':181 'analysi':120 'analyt':116 'api':85,113,184 'attach':94 'avail':212 'base':9,22,62,73,158 'base-network' 'beyond':203 'broader':110 'call':47 'caller':92 'categori':168 'challeng':66,194 'classif':122 'convers':139 'data':4,17,115 'decim':78 'document':202,237 'embed':123 'endpoint':28,51,142,161,186 'equal':80 'estim':133 'exampl':209 'exchang':128 'explicit':173 'featur':183 'feed':127 'financ':124 'format':216 'gas':132 'generat':140 'geocod':137 'header':99 'host':108 'howev':195 'id':40 'infer':118,235 'inform':34,231 'infrastructur':135 'json':227 'key':86 'land':179,205 'like':225 'limit':89 'list':144,174 'live':188 'lowpaymentfee.com':30 'maxamountrequir':69 'micropay':7,20 'model':154 'network':63 'nft':2,15,32,38,219 'nft-ownership-query' 'no-api-key' 'openapi':199 'owner':220,229 'ownership':3,16,33 'page':180,206 'part':164 'pay':45 'pay-per-cal':44 'pay-per-call' 'payload':211 'payment':98,104,153 'per':12,25,46,82,147 'post':53 'post-endpoint' 'price':126 'proof':105 'proper':192 'protocol':49 'provid':107,177 'queri':1,14,221 'quot':131 'rate':88,129 'request':13,26,54,83,148 'request/response':210 'requir':91 'respons':215 'return':31,190,226 'schema':200 'sentiment':119 'settl':57 'simpli':93 'span':114 'specif':37,160 'suit':111 'summar':121 'though':169 'token':39,130 'token owner query' 'unit':74 'unknown':223 'usdc':59,76,156 'usdc-payment' 'use':155 'util':136 'valid':102,138 'via':5,18,42 'web3':125 'web3/nft':167 'x':97 'x-payment':96 'x402':6,19,48,65,103,152 'x402 NFT API' 'x402-micropayment'","prices":[{"id":"399c6abb-e3c5-4d54-9c76-eb69a3561c21","listingId":"6050629f-f48b-4438-b2ba-270e432630e7","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/99/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":"2026-04-21T18:32:32.201Z"}],"sources":[{"listingId":"6050629f-f48b-4438-b2ba-270e432630e7","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/nfts/99/owner","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:32.201Z","lastSeenAt":"2026-04-22T10:33:05.976Z"}],"details":{"listingId":"6050629f-f48b-4438-b2ba-270e432630e7","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/nfts/99/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 (USD Coin) on Base network","source_url":"https://lowpaymentfee.com/api/v1/nfts/99/owner"},{"claim":"All listed APIs are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/nfts/99/owner"}],"useCases":["Look up the current owner of a specific NFT programmatically","Integrate NFT ownership verification into agent workflows without API key management","Pay-per-call NFT data retrieval settled on Base L2"],"bestFor":["Agents needing on-demand NFT ownership data without subscription commitments","Developers prototyping Web3 apps who want instant API access with no signup","Micropayment-based workflows where per-call billing is preferred"],"notFor":["Bulk NFT ownership queries across many token IDs (only token 99 is addressed by this endpoint)","Users who need free or subscription-based NFT data APIs","Production systems requiring documented response schemas and SLAs"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:12:51.342Z"},"updatedAt":"2026-04-22T10:33:05.976Z"}}