{"id":"b5904a97-4f2a-430c-94ed-209faf11ee95","shortId":"ZDAfFj","kind":"x402","title":"Pay-per-call API platform on Base via x402 — data, AI, finance, and utility endpoints at $0.02/request.","tagline":"Pay-per-call API platform on Base via x402 — data, AI, finance, and utility endpoints at $0.02/request.","description":"lowpaymentfee.com is an x402-enabled API platform that offers a broad set of endpoints across 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 endpoints are priced at $0.02 per request, paid in USDC on the Base network with no API keys, rate limits, or commitments required.\n\nThe specific endpoint at `/api/v1/invoices/6` is listed as \"Premium API Access\" and returns a standard x402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the x402 exact scheme with a 300-second timeout. The endpoint accepts HTTP POST and returns application/json.\n\nDocumentation beyond the landing page is extremely sparse — the /docs, /pricing, /api, and /README pages all render only a \"Connect wallet\" prompt with no additional technical content. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The actual functionality behind the `/api/v1/invoices/6` path is unclear; it may be an invoice retrieval or generation endpoint, but this is not documented. The platform appears live and functional based on the 402 challenge response.","tags":[],"capabilities":["x402-payment","per-request-billing","usdc-base","data-analytics","sentiment-analysis","text-summarization","text-classification","embeddings","price-feeds","exchange-rates","gas-estimates","geocoding","no-api-key"],"categories":["ai","finance","data","infrastructure"],"synonyms":["pay-per-call API","x402 API","micropayment API","USDC API","Base network API","low fee API","crypto-paid API"],"warnings":["No OpenAPI specification or schema documentation available","All documentation pages (/docs, /pricing, /api, /README) render only 'Connect wallet' with no content","The specific purpose and expected request/response format of /api/v1/invoices/6 is undocumented","The breadth of advertised endpoints (16+ across 4 categories) cannot be verified from available material"],"endpointUrl":"https://lowpaymentfee.com/api/v1/invoices/6","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/6","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live and returns a valid x402 challenge, and the landing page lists available endpoints with pricing. However, there is no OpenAPI spec, no request/response schemas, no documentation beyond the homepage, and the specific purpose of /api/v1/invoices/6 is undocumented. This is effectively a stub 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'/api/v1/invoices/6':118,219 '/docs':182 '/pricing':183 '/readme':186 '/request':19,38 '0.02':18,37,95,146 '000':135 '0x8335':140 '20':134 '2913':141 '300':162 '402':246 '6':150 'Base network API' 'USDC API' 'accept':167 'access':124 'across':54 'actual':215 'addit':197 'ai':12,31,64 'analysi':68 'analyt':58 'api':5,24,45,107,123 'appear':239 'application/json':172 'avail':213 'base':8,27,103,136,143,243 'behind':217 'beyond':174 'broad':50 'call':4,23 'categori':56 'challeng':130,247 'classif':71 'commit':112 'connect':192 'content':199 'convers':88 'crypto-paid API' 'data':11,30,57,61 'data-analytics' 'decim':151 'document':173,208,236 'embed':72 'embeddings' 'enabl':44 'endpoint':16,35,53,91,116,166,231 'equal':145 'estim':82 'exact':158 'exampl':211 'exchang':77 'exchange-rates' 'export':62 'extrem':179 'feed':76 'financ':13,32,73 'four':55 'function':216,242 'gas':81 'gas-estimates' 'generat':89,230 'geocod':86 'geocoding' 'given':147 'http':168 'infrastructur':84 'insight':63 'invoic':227 'key':108 'land':176 'learn':66 'limit':110 'list':120 'live':240 'low fee API' 'lowpaymentfee.com':39 'machin':65 'made':154 'may':224 'metric':59 'micropayment API' 'network':104 'no-api-key' 'offer':48 'openapi':203 'page':177,187 'paid':98 'path':220 'pay':2,21 'pay-per-cal':1,20 'pay-per-call API' 'payload':212 'payment':152 'per':3,22,96 'per-request-billing' 'platform':6,25,46,238 'post':169 'premium':122 'price':75,93 'price-feeds' 'prompt':194 'quot':80 'rate':78,109 'render':189 'report':60 'request':97,131 'request/response':206 'requir':113 'respons':248 'retriev':228 'return':126,171 'schema':207 'scheme':159 'second':163 'sentiment':67 'sentiment-analysis' 'set':51 'spars':180 'spec':204 'specif':115 'standard':128 'summar':70 'technic':198 'text':69 'text-classification' 'text-summarization' 'timeout':164 'token':79 'unclear':222 'unit':137 'usdc':100,139,148 'usdc-base' 'util':15,34,85 'valid':87 'via':9,28,155 'wallet':193 'web3':74 'x402':10,29,43,129,157 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"dd2b62f8-a8d2-4be0-a245-e4830bb77dd4","listingId":"b5904a97-4f2a-430c-94ed-209faf11ee95","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/6","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:35:06.057Z"}],"sources":[{"listingId":"b5904a97-4f2a-430c-94ed-209faf11ee95","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/invoices/6","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:35:06.057Z","lastSeenAt":"2026-04-23T00:31:04.822Z"}],"details":{"listingId":"b5904a97-4f2a-430c-94ed-209faf11ee95","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/invoices/6 \\\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":"All endpoints are priced at $0.02 per request with no API keys, rate limits, or commitments","source_url":"https://lowpaymentfee.com"},{"claim":"Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"Payment is in USDC on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"x402 challenge returns maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base","source_url":"https://lowpaymentfee.com/api/v1/invoices/6"}],"useCases":["Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key signup","Fetching real-time financial data like token quotes, gas estimates, and exchange rates on a per-call basis","Running data analytics queries and exporting reports with pay-as-you-go pricing","Using utility services like geocoding and validation without subscription commitments"],"bestFor":["Developers who want instant API access without registration or API keys","Agents and bots that can settle payments in USDC on Base via x402","Low-volume or sporadic API consumers who prefer per-request pricing over subscriptions"],"notFor":["High-volume production workloads where $0.02/request adds up significantly","Users who need detailed API documentation, SDKs, or guaranteed SLAs","Developers without access to USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:51.788Z"},"updatedAt":"2026-04-23T00:31:04.822Z"}}