{"id":"dc2bfd6c-490f-403e-aac5-b86889b37094","shortId":"MDwrSH","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 catalog of pay-per-request 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.\n\nThe specific endpoint being listed here — `/api/v1/invoices/42` — is described as \"Premium API Access\" and returns a live x402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) on Base. The payment scheme is \"exact,\" meaning a single per-call payment is required. The endpoint accepts HTTP POST and returns application/json. No API keys or rate limits are advertised; access is gated entirely by the x402 payment protocol.\n\nDocumentation is extremely sparse. The docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no detailed description of what the `/api/v1/invoices/42` endpoint actually returns. The broader site catalog suggests a variety of services, but the specific behavior of this invoice endpoint is unclear from available materials.","tags":[],"capabilities":["x402-payment","per-request-billing","usdc-base","json-response","http-post","no-api-key","no-rate-limit"],"categories":["api-marketplace","finance"],"synonyms":["pay-per-call API","x402 API","micropayment API","USDC API","Base network API","lowpaymentfee","invoice API","crypto-paid API"],"warnings":["Documentation pages (/docs, /api, /pricing, /README) all render only 'Connect wallet' with no substantive content.","No OpenAPI or schema available; request and response formats for this endpoint are unknown.","The specific purpose and output of /api/v1/invoices/42 is unclear — 'Premium API Access' is generic.","The broader site lists many endpoints but none have documented schemas or example payloads."],"endpointUrl":"https://lowpaymentfee.com/api/v1/invoices/42","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/42","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, confirming it is operational. However, documentation is essentially nonexistent — all doc pages show only 'Connect wallet.' There is no OpenAPI schema, no request/response examples, and the purpose of the specific /api/v1/invoices/42 endpoint is not explained beyond the generic label 'Premium API Access.' The listing is largely a 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'/request':19,38 '0.02':18,37,99,138 '000':132 '20':131 'Base network API' 'USDC API' 'accept':157 'access':121,171 'across':58 'actual':219 'advertis':170 'ai':12,31,68 'analysi':72 'analyt':62 'api':5,24,45,120,164,186 'application/json':162 'avail':241 'base':8,27,107,133,140 'behavior':233 'broad':50 'broader':222 'call':4,23,151 'catalog':51,224 'categori':60 'challeng':127 'classif':75 'connect':195 'content':201 'convers':92 'crypto-paid API' 'data':11,30,61,65 'describ':117 'descript':213 'detail':212 'doc':185 'document':180 'embed':76 'enabl':44 'endpoint':16,35,57,95,111,156,218,237 'entir':174 'estim':86 'exact':145 'exampl':209 'exchang':81 'export':66 'extrem':182 'feed':80 'financ':13,32,77 'four':59 'gas':85 'gate':173 'generat':93 'geocod':90 'http':158 'http-post' 'i.e':137 'infrastructur':88 'insight':67 'invoic':236 'invoice API' 'json-response' 'key':165 'learn':70 'limit':168 'list':113 'live':125 'lowpaymentfee' 'lowpaymentfee.com':39 'machin':69 'materi':242 'mean':146 'metric':63 'micropayment API' 'network':108 'no-api-key' 'no-rate-limit' 'offer':48 'openapi':205 'page':190 'paid':102 'pay':2,21,54 'pay-per-cal':1,20 'pay-per-call API' 'pay-per-request':53 'payment':142,152,178 'per':3,22,55,100,150 'per-cal':149 'per-request-billing' 'platform':6,25,46 'post':159 'premium':119 'price':79,97,187 'prompt':197 'protocol':179 'quot':84 'rate':82,167 'readm':189 'render':192 'report':64 'request':56,101,128 'request/response':208 'requir':154 'return':123,161,220 'schema':206 'scheme':143 'sentiment':71 'servic':229 'singl':148 'site':223 'spars':183 'specif':110,232 'substant':200 'suggest':225 'summar':74 'text':73 'token':83 'unclear':239 'unit':134 'usdc':104,136 'usdc-base' 'util':15,34,89 'valid':91 'varieti':227 'via':9,28 'wallet':196 'web3':78 'x402':10,29,43,126,177 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"e95a65a3-9a34-4c4c-9315-c493b11f3b79","listingId":"dc2bfd6c-490f-403e-aac5-b86889b37094","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/42","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:38:16.442Z"}],"sources":[{"listingId":"dc2bfd6c-490f-403e-aac5-b86889b37094","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/invoices/42","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:38:16.442Z","lastSeenAt":"2026-04-23T10:30:29.795Z"}],"details":{"listingId":"dc2bfd6c-490f-403e-aac5-b86889b37094","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/invoices/42 \\\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 live x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/invoices/42"},{"claim":"All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on the Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The site offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/invoices/42"}],"useCases":["Accessing premium API data without signing up for an account or managing API keys","Making one-off paid API calls from autonomous agents using x402 on Base","Retrieving invoice or financial data via a single micropayment"],"bestFor":["Agents or developers who want keyless, pay-as-you-go API access","Use cases requiring low-friction micropayments ($0.02/call) on Base","Scenarios where no subscription or rate-limit management is desired"],"notFor":["Users who need detailed API documentation or guaranteed SLAs before integrating","High-volume use cases where per-call pricing may be less economical than bulk plans","Anyone without access to USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:42.443Z"},"updatedAt":"2026-04-23T10:30:29.795Z"}}