{"id":"9c772c1a-09f9-41bd-b328-dfeba68e708d","shortId":"bfzmPs","kind":"x402","title":"Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.","tagline":"Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.","description":"lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/invoices/31` is listed as \"Premium API Access\" and charges up to $0.02 per call (20,000 base units of USDC with 6 decimals). The platform advertises no API keys, no rate limits, and instant access — callers simply attach an x402 payment header to each request.\n\nThe site organizes its endpoints into four categories: 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 listed endpoints share the same $0.02 per-request pricing.\n\nDocumentation is extremely sparse — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI schema, no request/response examples, and no description of what the `/api/v1/invoices/31` endpoint specifically returns. The x402 challenge confirms the endpoint is live and accepts POST requests, but the actual payload format and response structure are unknown.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","data-analytics","ai-inference","sentiment-analysis","text-summarization","classification","embeddings","finance-data","exchange-rates","gas-estimates","geocoding","validation"],"categories":["api-platform","llm","finance","geo"],"synonyms":["low payment fee","micropayment API","x402 API","pay-per-call API","USDC API","Base network API","premium API access"],"warnings":["No OpenAPI schema or request/response documentation available","Docs, API, pricing, and README pages all render only 'Connect wallet' with no content","The specific function of /api/v1/invoices/31 is undocumented — it is unclear what data or service it provides","No examples of expected input or output formats"],"endpointUrl":"https://lowpaymentfee.com/api/v1/invoices/31","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/invoices/31","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The x402 challenge confirms the endpoint is live and pricing is clear ($0.02 USDC on Base), but there is zero documentation on request/response schemas, no OpenAPI spec, and the docs pages are empty. The specific purpose of /api/v1/invoices/31 is unclear beyond the generic label 'Premium API 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'/request':19,38 '0.02':18,37,80,161 '000':84 '20':83 '6':90 'Base network API' 'USDC API' 'accept':216 'access':75,103 'actual':221 'advertis':94 'ai':12,31,129 'ai-inference' 'analysi':133 'analyt':123 'api':5,24,45,74,96,172 'attach':106 'base':8,27,63,85 'broad':50 'call':4,23,82 'caller':104 'catalog':51 'categori':121 'challeng':209 'charg':77 'classif':136 'classification' 'confirm':210 'connect':181 'convers':153 'cover':10,29 'data':11,30,122,126 'data-analytics' 'decim':91 'descript':199 'detail':188 'doc':171 'document':166 'embed':137 'embeddings' 'enabl':44 'endpoint':16,35,57,67,118,157,204,212 'estim':147 'exampl':196 'exchang':142 'exchange-rates' 'export':127 'extrem':168 'feed':141 'financ':13,32,138 'finance-data' 'format':223 'four':120 'gas':146 'gas-estimates' 'generat':154 'geocod':151 'geocoding' 'header':110 'infrastructur':149 'insight':128 'instant':102 'key':97 'learn':131 'limit':100 'list':71,156 'live':214 'low payment fee' 'lowpaymentfee.com':39 'machin':130 'metric':124 'micropayment API' 'network':64 'offer':48 'openapi':192 'organ':116 'page':176 'pay':2,21,54 'pay-per-cal':1,20 'pay-per-call API' 'pay-per-request':53 'payload':222 'payment':109 'per':3,22,55,81,163 'per-request':162 'platform':6,25,46,93 'post':217 'premium':73 'premium API access' 'price':140,165,173 'prompt':183 'quot':145 'rate':99,143 'readm':175 'render':178 'report':125 'request':56,113,164,218 'request/response':195 'respons':225 'return':206 'schema':193 'sentiment':132 'sentiment-analysis' 'settl':58 'share':158 'simpli':105 'site':115 'spars':169 'specif':66,205 'structur':226 'summar':135 'technic':187 'text':134 'text-summarization' 'token':144 'unit':86 'unknown':228 'usdc':9,28,60,88 'usdc-base' 'util':15,34,150 'valid':152 'validation' 'wallet':182 'web3':139 'x402':43,108,208 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"35aa8368-1ad4-45bf-9e67-37e058c9bdda","listingId":"9c772c1a-09f9-41bd-b328-dfeba68e708d","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/invoices/31","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:37:54.184Z"}],"sources":[{"listingId":"9c772c1a-09f9-41bd-b328-dfeba68e708d","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/invoices/31","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:37:54.184Z","lastSeenAt":"2026-04-23T14:00:42.387Z"}],"details":{"listingId":"9c772c1a-09f9-41bd-b328-dfeba68e708d","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/invoices/31 \\\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 challenge with maxAmountRequired of 20000 in USDC (asset 0x8335…) on Base network","source_url":"https://lowpaymentfee.com/api/v1/invoices/31"},{"claim":"All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management","Fetching real-time finance data like token quotes, exchange rates, and gas estimates on a per-call basis","Running utility operations such as geocoding, validation, and data conversion with micropayments","Integrating pay-per-use data analytics and reporting into agent workflows"],"bestFor":["Agents or developers who want keyless, pay-per-request API access","Low-volume or bursty workloads where subscription pricing is wasteful","Crypto-native applications already operating on Base with USDC"],"notFor":["Users needing detailed API documentation or guaranteed SLAs before integrating","High-volume production workloads where $0.02/request adds up significantly","Developers who cannot transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:43.554Z"},"updatedAt":"2026-04-23T14:00:42.387Z"}}