{"id":"d3a1ef53-71fe-4e96-9a26-4124d6cfcd1f","shortId":"kPruJT","kind":"x402","title":"x402-gated premium API endpoint on Base, pay $0.02 per request in USDC.","tagline":"x402-gated premium API endpoint on Base, pay $0.02 per request in USDC.","description":"This endpoint at `/api/v1/cards/57` is part of the lowpaymentfee.com platform, which offers a collection of x402-protocol pay-per-request APIs spanning data & analytics, AI & machine learning, finance & Web3, and infrastructure utilities. The specific resource at `/cards/57` is labeled \"Premium API Access\" but its exact functionality is not documented beyond that label. It is one of many endpoints on the platform, all priced uniformly at $0.02 per call.\n\nPayment is handled via the x402 protocol on the Base network using USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The challenge advertises a `maxAmountRequired` of 20,000 base units, which at 6 decimals equals $0.02. No API keys or rate limits are required — callers simply attach an `X-PAYMENT` header with a valid x402 payment proof. The endpoint accepts HTTP POST requests and returns `application/json`.\n\nThe broader platform lists endpoints for sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, geocoding, validation, conversion, and data export, all at the same $0.02 price point. However, documentation is extremely sparse — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further technical detail. Without documentation or schema definitions for request/response bodies, it is unclear what parameters `/api/v1/cards/57` expects or what it returns.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","json-api","no-api-key","http-post"],"categories":["api","misc"],"synonyms":["premium API","paid API","x402 endpoint","lowpaymentfee","USDC API","Base network API","micropayment API","cards API"],"warnings":["The exact purpose and functionality of /api/v1/cards/57 ('Premium API Access') is not documented anywhere in the crawled material.","All documentation pages (docs, API, pricing, README) render only 'Connect wallet' with no technical content.","No request or response schema is available — callers cannot know what parameters to send or what to expect back.","The endpoint path '/api/v1/cards/57' does not match any of the listed API categories on the homepage, suggesting it may be a test or placeholder resource."],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/57","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/57","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but the specific functionality of /api/v1/cards/57 is undocumented. No request/response schemas, no examples, and all documentation pages return only 'Connect wallet' with no content. This is effectively a stub 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'/cards/57':67 '0.02':10,24,96,129,187 '000':121 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':113 '20':120 '6':126 'Base network API' 'USDC API' 'accept':154 'access':72 'advertis':116 'ai':55 'analysi':168 'analyt':54 'api':5,19,51,71,131,197 'application/json':160 'attach':140 'base':8,22,108,122 'beyond':80 'bodi':221 'broader':162 'call':98 'caller':138 'cards API' 'challeng':115 'classif':171 'collect':42 'connect':206 'contract':112 'convers':179 'data':53,181 'decim':127 'definit':218 'detail':213 'doc':196 'document':79,191,215 'embed':172 'endpoint':6,20,30,88,153,165 'equal':128 'exact':75 'exchang':175 'expect':228 'export':182 'extrem':193 'feed':174 'financ':58 'function':76 'gate':3,17 'geocod':177 'handl':101 'header':145 'howev':190 'http':155 'http-post' 'infrastructur':61 'json-api' 'key':132 'label':69,82 'learn':57 'limit':135 'list':164 'lowpaymentfee' 'lowpaymentfee.com':37 'machin':56 'mani':87 'maxamountrequir':118 'micropayment API' 'network':109 'no-api-key' 'offer':40 'one':85 'page':201 'paid API' 'paramet':226 'part':34 'pay':9,23,48 'pay-per-request':47 'payment':99,144,150 'per':11,25,49,97 'platform':38,91,163 'point':189 'post':156 'premium':4,18,70 'premium API' 'price':93,173,188,198 'prompt':208 'proof':151 'protocol':46,105 'rate':134,176 'readm':200 'render':203 'request':12,26,50,157 'request/response':220 'requir':137 'resourc':65 'return':159,232 'schema':217 'sentiment':167 'simpli':139 'span':52 'spars':194 'specif':64 'summar':170 'technic':212 'text':169 'unclear':224 'uniform':94 'unit':123 'usdc':14,28,111 'usdc-base' 'use':110 'util':62 'valid':148,178 'via':102 'wallet':207 'web3':59 'without':214 'x':143 'x-payment':142 'x402':2,16,45,104,149 'x402 endpoint' 'x402-gated':1,15 'x402-payment' 'x402-protocol':44","prices":[{"id":"b8302e33-218a-404e-bf13-9ff40aac3fc0","listingId":"d3a1ef53-71fe-4e96-9a26-4124d6cfcd1f","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/57","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:40.642Z"}],"sources":[{"listingId":"d3a1ef53-71fe-4e96-9a26-4124d6cfcd1f","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/57","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:40.642Z","lastSeenAt":"2026-04-22T10:01:40.338Z"}],"details":{"listingId":"d3a1ef53-71fe-4e96-9a26-4124d6cfcd1f","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/cards/57 \\\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 endpoint returns a 402 challenge with maxAmountRequired of 20000 base units in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/cards/57"},{"claim":"All APIs on the platform are priced at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/cards/57"},{"claim":"Documentation, API, pricing, and README pages all show only 'Connect wallet' with no further content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Accessing a premium data or service endpoint with per-request USDC micropayments","Integrating pay-per-call APIs without managing API keys or subscriptions","Agent-driven API consumption using x402 payment protocol"],"bestFor":["Developers wanting zero-commitment pay-per-use API access","AI agents that can settle x402 payments on Base","Users who prefer crypto micropayments over subscription billing"],"notFor":["Anyone needing detailed API documentation or request/response schemas before integrating","Use cases requiring free or high-volume bulk access at discounted rates"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:26.626Z"},"updatedAt":"2026-04-22T10:01:40.338Z"}}