{"id":"afd6dcc2-ad60-4722-97d9-9cbc9a64da59","shortId":"Dqk57g","kind":"x402","title":"NFT metadata endpoint on Base, pay-per-call via x402 with USDC at $0.02/request.","tagline":"NFT metadata endpoint on Base, pay-per-call via x402 with USDC at $0.02/request.","description":"This endpoint at lowpaymentfee.com serves NFT metadata for token ID 21 via a POST request, gated by the x402 payment protocol. Each call costs $0.02 in USDC on the Base network (maxAmountRequired of 20,000 base units with 6 decimals = $0.02). No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof to access the resource.\n\nThe provider operates a broader platform offering dozens of pay-per-call 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 share the same $0.02/request pricing model and settle on the Base network using USDC.\n\nThis specific endpoint returns application/json content (as declared in the x402 challenge's mimeType field). The exact schema of the NFT metadata response is not documented, so callers should expect a standard NFT metadata JSON object but should handle unknown fields gracefully. The endpoint is live and returning a proper 402 challenge with x402 version 1.","tags":[],"capabilities":["nft-metadata","x402-payment","usdc-settlement","base-network","pay-per-call","no-api-key","post-endpoint"],"categories":["web3","nft"],"synonyms":["NFT metadata API","token metadata","NFT token info","x402 NFT endpoint","Base USDC API","pay-per-request NFT","lowpaymentfee NFT"],"warnings":["No OpenAPI or schema documentation available for request or response bodies","Endpoint is scoped to a single NFT token ID (21); unclear if other token IDs are available at similar paths","No crawled documentation beyond the landing page listing; /api, /pricing, and /README pages returned only a wallet-connect prompt","The actual content returned by this NFT metadata endpoint is unknown — response structure is not documented"],"endpointUrl":"https://lowpaymentfee.com/api/v1/nfts/21/metadata","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/metadata","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.400","qualityRationale":"The endpoint is live and returns a valid x402 402 challenge with clear pricing and network info. However, there is no OpenAPI schema, no documented request/response body, no examples, and the NFT metadata content is entirely unknown. The endpoint is scoped to a single token ID with no broader 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'0.02':15,31,57,73,145 '000':67 '1':212 '20':66 '21':43 '402':207 '6':71 'Base USDC API' 'NFT metadata API' 'NFT token info' 'access':97 'ai/ml':117 'analysi':120 'analyt':116 'api':75,113 'application/json':161 'attach':84 'base':5,21,62,68,153 'base-network' 'broader':104 'call':9,25,55,112 'caller':82,184 'challeng':168,208 'classif':122 'content':162 'convers':138 'cost':56 'data':115 'decim':72 'declar':164 'document':182 'dozen':107 'embed':123 'endpoint':3,19,34,141,159,200 'estim':132 'exact':173 'exchang':127 'expect':186 'feed':126 'field':171,197 'finance/web3':124 'gas':131 'gate':48 'generat':139 'geocod':136 'grace':198 'handl':195 'header':89 'id':42 'infer':118 'infrastructur':134 'json':191 'key':76 'limit':79 'live':202 'lowpaymentfee NFT' 'lowpaymentfee.com':36 'maxamountrequir':64 'metadata':2,18,39,178,190 'mimetyp':170 'model':148 'network':63,154 'nft':1,17,38,177,189 'nft-metadata' 'no-api-key' 'object':192 'offer':106 'oper':102 'pay':7,23,110 'pay-per-cal':6,22,109 'pay-per-call' 'pay-per-request NFT' 'payment':52,88,94 'per':8,24,111 'platform':105 'post':46 'post-endpoint' 'price':125,147 'proof':95 'proper':206 'protocol':53 'provid':101 'quot':130 'rate':78,128 'request':47 'requir':81 'resourc':99 'respons':179 'return':160,204 'schema':174 'sentiment':119 'serv':37 'settl':150 'share':142 'simpli':83 'span':114 'specif':158 'standard':188 'summar':121 'token':41,129 'token metadata' 'unit':69 'unknown':196 'usdc':13,29,59,156 'usdc-settlement' 'use':155 'util':135 'valid':92,137 'version':211 'via':10,26,44 'x':87 'x-payment':86 'x402':11,27,51,93,167,210 'x402 NFT endpoint' 'x402-payment'","prices":[{"id":"9c75cc9d-0527-4adb-9ac4-ae8f3fad55f6","listingId":"afd6dcc2-ad60-4722-97d9-9cbc9a64da59","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/metadata","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:27.829Z"}],"sources":[{"listingId":"afd6dcc2-ad60-4722-97d9-9cbc9a64da59","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/nfts/21/metadata","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:27.829Z","lastSeenAt":"2026-04-22T20:02:13.018Z"}],"details":{"listingId":"afd6dcc2-ad60-4722-97d9-9cbc9a64da59","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/nfts/21/metadata \\\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 x402 version 1 challenge requiring USDC payment on Base network","source_url":"https://lowpaymentfee.com/api/v1/nfts/21/metadata"},{"claim":"maxAmountRequired is 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) which equals $0.02","source_url":"https://lowpaymentfee.com/api/v1/nfts/21/metadata"},{"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 platform offers additional API categories including Data & Analytics, AI & ML, Finance & Web3, and Infrastructure","source_url":"https://lowpaymentfee.com"}],"useCases":["Retrieving on-chain NFT metadata for display in wallets or marketplaces","Programmatic access to NFT attributes for indexing or analytics","Agent-driven NFT data retrieval with automatic micropayment settlement"],"bestFor":["Developers needing NFT metadata without managing API keys","AI agents that can settle x402 payments autonomously","Low-volume or sporadic NFT metadata lookups where per-call pricing is economical"],"notFor":["High-volume bulk NFT metadata scraping (no documented batch endpoint)","Users who need metadata for arbitrary token IDs (this endpoint is scoped to token 21)"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:12:58.82Z"},"updatedAt":"2026-04-22T20:02:13.018Z"}}