{"id":"cf649774-1e60-45ae-b243-2e0d5828b9d6","shortId":"REuhuv","kind":"x402","title":"x402-gated premium API endpoint on Base, pay-per-request with USDC.","tagline":"x402-gated premium API endpoint on Base, pay-per-request with USDC.","description":"This endpoint at `/api/v1/cards/43` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities. The specific endpoint is labeled \"Premium API Access\" and accepts POST requests, returning JSON responses. Payment is settled on the Base network using USDC (contract 0x8335…2913) via the x402 exact-payment scheme.\n\nThe x402 challenge advertises a maxAmountRequired of 20,000 base units. Since USDC uses 6 decimals, this translates to $0.02 per request, consistent with the site-wide pricing of $0.02/request. The platform advertises no API keys, no rate limits, and instant access — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nHowever, the specific functionality behind `/api/v1/cards/43` is unclear. The site's landing page lists various categorized endpoints (analytics, AI, finance, utilities) but does not mention a `/cards/43` route. There is no OpenAPI spec, no detailed documentation (the /docs, /pricing, and /README pages all render only a \"Connect wallet\" prompt with no substantive content), and no request/response schema beyond the x402 challenge's outputSchema stub. The actual data or service returned by this endpoint is unknown.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","json-response","post-method"],"categories":["api","payments"],"synonyms":["lowpaymentfee","x402 api","pay per call api","USDC micropayment api","base network api","premium api access","cards endpoint"],"warnings":["The specific functionality of /api/v1/cards/43 is unknown — it does not appear in the site's listed API catalog","No OpenAPI spec or request/response schema available","All documentation pages (/docs, /pricing, /README) render only a 'Connect wallet' prompt with no content","Cannot verify what data or service is returned without making a paid request"],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/43","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/cards/43","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.250","qualityRationale":"The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02/request in USDC on Base), but there is no documentation, no OpenAPI spec, no request/response examples, and the actual functionality of /api/v1/cards/43 is completely undocumented. The docs, pricing, and README pages are all empty beyond a wallet-connect 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'/cards/43':178 '/docs':189 '/pricing':190 '/readme':192 '/request':125 '0.02':113,124 '000':102 '0x8335':85 '20':101 '2913':86 '6':108 'USDC micropayment api' 'accept':69 'access':67,137 'actual':217 'advertis':97,128 'ai':170 'ai/ml':53 'analyt':52,169 'api':5,19,49,66,130 'attach':140 'base':8,22,80,103 'base network api' 'base-network' 'behind':156 'beyond':209 'call':48 'caller':138 'cards endpoint' 'categor':167 'challeng':96,212 'collect':40 'connect':198 'consist':116 'content':204 'contract':84 'data':51,56,218 'decim':109 'detail':186 'document':187 'endpoint':6,20,30,62,168,224 'exact':91 'exact-pay':90 'financ':171 'finance/web3':55 'function':155 'gate':3,17 'header':145 'howev':152 'infer':54 'infrastructur':58 'instant':136 'json':73 'json-response' 'key':131 'label':64 'land':163 'limit':134 'list':165 'lowpaymentfee' 'lowpaymentfee.com':37 'maxamountrequir':99 'mention':176 'network':81 'openapi':183 'outputschema':214 'page':164,193 'part':34 'pay':10,24,46 'pay per call api' 'pay-per-cal':45 'pay-per-request':9,23 'payment':75,92,144,150 'per':11,25,47,114 'platform':38,127 'post':70 'post-method' 'premium':4,18,65 'premium api access' 'price':122 'prompt':200 'proof':151 'protocol':44 'rate':133 'render':195 'request':12,26,71,115 'request/response':207 'respons':74 'return':72,221 'rout':179 'schema':208 'scheme':93 'servic':220 'settl':77 'simpli':139 'sinc':105 'site':120,161 'site-wid':119 'span':50 'spec':184 'specif':61,154 'stub':215 'substant':203 'translat':111 'unclear':159 'unit':104 'unknown':226 'usdc':14,28,83,106 'usdc-settlement' 'use':82,107 'util':59,172 'valid':148 'various':166 'via':87 'wallet':199 'wide':121 'x':143 'x-payment':142 'x402':2,16,43,89,95,149,211 'x402 api' 'x402-gated':1,15 'x402-payment' 'x402-protocol':42","prices":[{"id":"7df7545c-5e77-49f2-abd8-12f462708ab3","listingId":"cf649774-1e60-45ae-b243-2e0d5828b9d6","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/cards/43","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:33.407Z"}],"sources":[{"listingId":"cf649774-1e60-45ae-b243-2e0d5828b9d6","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/43","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:33.407Z","lastSeenAt":"2026-04-22T15:01:10.721Z"}],"details":{"listingId":"cf649774-1e60-45ae-b243-2e0d5828b9d6","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/cards/43 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The x402 challenge returns maxAmountRequired of 20000 base units in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/cards/43"},{"claim":"Site-wide pricing is $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/cards/43"}],"useCases":["Programmatic access to an unknown premium data or service endpoint via x402 micropayment","Demonstrating x402 pay-per-call integration on the Base network","Agent-driven API consumption without API keys using on-chain USDC payments"],"bestFor":["Developers experimenting with x402 protocol payments","Agents that can settle USDC payments on Base","Use cases requiring keyless, pay-as-you-go API access"],"notFor":["Users who need clear documentation of request/response schemas before integrating","Applications requiring free or subscription-based API access","Anyone needing to understand exactly what data this endpoint returns before paying"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:26.975Z"},"updatedAt":"2026-04-22T15:01:10.721Z"}}