{"id":"465bc0bd-d54f-4ae8-9d68-bdc8fa5da446","shortId":"6ABuPw","kind":"x402","title":"x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.","tagline":"x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.","description":"lowpaymentfee.com is an x402-protocol API platform that gates access to a variety of endpoints behind per-request micropayments settled in USDC on the Base network. The specific endpoint `/api/v1/cards/18` is listed as \"Premium API Access\" and requires a payment of up to 20,000 base units of USDC (i.e., $0.02) per call. Payment is made via the x402 exact scheme with no API keys, no rate limits, and no upfront commitments required.\n\nThe broader platform advertises four categories of endpoints: Data & Analytics (metrics, reports, data export, insights), AI & Machine Learning (sentiment analysis, text 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 the same $0.02/request price point. However, the specific endpoint being listed here (`/api/v1/cards/18`) does not clearly map to any of these named categories — it sits under a `/cards/` path whose purpose is not documented.\n\nDocumentation is extremely sparse. The docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI schema, no request/response examples, and no description of what `/api/v1/cards/18` actually returns. The endpoint is confirmed live (returns a proper 402 x402 challenge), but without documentation it is unclear what data or functionality it provides.","tags":[],"capabilities":["x402-payment","usdc-base","per-request-micropayment","json-response","post-method"],"categories":["api-platform","misc"],"synonyms":["lowpaymentfee","low payment fee API","x402 micropayment API","pay-per-call API","Base USDC API","cards endpoint"],"warnings":["The /api/v1/cards/18 path does not correspond to any documented endpoint on the platform's landing page","All documentation pages (docs, API, pricing, README) render only 'Connect wallet' with no usable content","No OpenAPI schema or request/response examples are available","The actual data or functionality returned by this endpoint is completely undocumented"],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/18","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/18","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.250","qualityRationale":"The endpoint is confirmed live with a valid 402 x402 challenge, but there is no documentation, no OpenAPI schema, no request/response examples, and the /cards/18 path is not described anywhere on the site. The purpose of this specific endpoint is 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'/cards':184 '/request':17,34,159 '0.02':16,33,87,158 '000':81 '20':80 '402':237 'Base USDC API' 'access':45,72 'actual':227 'advertis':113 'ai':10,27,125 'analysi':129 'analyt':119 'api':4,21,41,71,100,197 'base':7,24,61,82 'behind':51 'broader':111 'call':89 'cards endpoint' 'categori':115,179 'challeng':239 'classif':132 'clear':172 'commit':108 'confirm':232 'connect':206 'content':212 'convers':149 'data':9,26,118,122,247 'descript':223 'doc':196 'document':190,191,242 'embed':133 'endpoint':14,31,50,65,117,152,165,230 'estim':143 'exact':96 'exampl':220 'exchang':138 'export':123 'extrem':193 'feed':137 'financ':11,28,134 'four':114 'function':249 'gas':142 'gate':3,20,44 'generat':150 'geocod':147 'howev':162 'i.e':86 'infrastructur':145 'insight':124 'json-response' 'key':101 'learn':127 'limit':104 'list':68,154,167 'live':233 'low payment fee API' 'lowpaymentfee' 'lowpaymentfee.com':35 'machin':126 'made':92 'map':173 'metric':120 'micropay':55 'name':178 'network':62 'offer':8,25 'openapi':216 'page':201 'path':185 'pay-per-call API' 'payment':76,90 'per':53,88 'per-request':52 'per-request-micropayment' 'platform':5,22,42,112 'point':161 'post-method' 'premium':70 'price':136,160,198 'prompt':208 'proper':236 'protocol':40 'provid':251 'purpos':187 'quot':141 'rate':103,139 'readm':200 'render':203 'report':121 'request':54 'request/response':219 'requir':74,109 'return':228,234 'schema':217 'scheme':97 'sentiment':128 'settl':56 'sit':181 'spars':194 'specif':64,164 'summar':131 'text':130 'token':140 'unclear':245 'unit':83 'upfront':107 'usdc':58,85 'usdc-base' 'util':13,30,146 'valid':148 'varieti':48 'via':93 'wallet':207 'web3':135 'whose':186 'without':241 'x402':2,19,39,95,238 'x402 micropayment API' 'x402-gated':1,18 'x402-payment' 'x402-protocol':38","prices":[{"id":"dfc73ee6-4619-4735-96dd-0943b24ff12f","listingId":"465bc0bd-d54f-4ae8-9d68-bdc8fa5da446","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/18","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:20.755Z"}],"sources":[{"listingId":"465bc0bd-d54f-4ae8-9d68-bdc8fa5da446","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/18","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:20.755Z","lastSeenAt":"2026-04-22T12:00:58.336Z"}],"details":{"listingId":"465bc0bd-d54f-4ae8-9d68-bdc8fa5da446","quickStartSnippet":"# The endpoint returns 402 with an x402 challenge.\n# Use an x402-compatible client to pay and access:\ncurl -X POST https://lowpaymentfee.com/api/v1/cards/18 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-token>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/cards/18"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/cards/18"},{"claim":"Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"Platform lists endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Accessing gated API resources with per-request USDC micropayments on Base","Agent-driven API consumption without API keys or subscriptions","Programmatic access to an unknown /cards/18 resource via x402 protocol"],"bestFor":["Developers experimenting with x402 micropayment protocol","Agents that can settle USDC payments on Base network","Use cases requiring keyless, pay-per-call API access"],"notFor":["Users who need documented, well-specified API contracts before integrating","Applications requiring free or subscription-based access patterns","Anyone needing to understand exactly what /cards/18 returns before paying"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:27.603Z"},"updatedAt":"2026-04-22T12:00:58.336Z"}}