{"id":"01882711-bd41-422e-8f8e-cbb3e286a0f8","shortId":"Zhtdm2","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 via the x402 protocol.\n\nThe specific endpoint at `/api/v1/invoices/4` is listed as \"Premium API Access\" and its x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the `exact` scheme with a 300-second timeout. No API keys or rate limits are required — callers simply attach an X-PAYMENT header to each request.\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/4` endpoint actually returns. The platform's landing page lists many endpoints but provides no technical documentation for any of them. The endpoint is live (returns a valid 402 challenge), but the actual functionality behind this specific invoice endpoint is unclear.","tags":[],"capabilities":["x402-payment","pay-per-request","usdc-base","data-analytics","ai-inference","sentiment-analysis","text-summarization","classification","embeddings","finance-data","exchange-rates","geocoding","crypto-gas-estimates"],"categories":["api-platform","llm","finance","geo"],"synonyms":["x402 API","pay per call API","micropayment API","USDC API","Base network API","lowpaymentfee","low payment fee","crypto API access"],"warnings":["No OpenAPI or schema documentation available for any endpoint","All documentation pages (docs, API, pricing, README) render only 'Connect wallet' with no content","The specific purpose and response format of /api/v1/invoices/4 is undocumented","The platform lists many endpoints but none have detailed technical docs"],"endpointUrl":"https://lowpaymentfee.com/api/v1/invoices/4","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/4","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 402 challenge, but there is no OpenAPI schema, no request/response examples, and no meaningful documentation beyond the landing page listing. The actual purpose of the /api/v1/invoices/4 endpoint is unclear. Docs pages are empty (wallet-connect only). This is effectively a stub 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'land':225 'learn':70 'limit':167 'list':119,227 'live':242 'low payment fee' 'lowpaymentfee' 'lowpaymentfee.com':39 'machin':69 'made':152 'mani':228 'maxamountrequir':130 'metric':63 'micropayment API' 'network':108 'offer':48 'openapi':206 'page':191,226 'paid':102 'pay':2,21,54 'pay per call API' 'pay-per-cal':1,20 'pay-per-request':53 'payment':150,176 'per':3,22,55,100 'platform':6,25,46,223 'premium':121 'price':79,97,188 'prompt':198 'protocol':112 'provid':231 'quot':84 'rate':82,166 'readm':190 'render':193 'report':64 'request':56,101,180 'request/response':209 'requir':169 'return':221,243 'schema':207 'scheme':156 'second':160 'sentiment':71 'sentiment-analysis' 'simpli':171 'spars':184 'specif':114,254 'substant':201 'summar':74 'technic':233 'text':73 'text-summarization' 'timeout':161 'token':83 'unclear':258 'unit':135 'usdc':104,137,146 'usdc-base' 'util':15,34,89 'valid':91,245 'via':9,28,109,153 'wallet':197 'web3':78 'x':175 'x-payment':174 'x402':10,29,43,111,126 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"bc80c364-add0-44e1-bbc8-3189d75026f1","listingId":"01882711-bd41-422e-8f8e-cbb3e286a0f8","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/4","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:35:34.900Z"}],"sources":[{"listingId":"01882711-bd41-422e-8f8e-cbb3e286a0f8","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/invoices/4","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:35:34.900Z","lastSeenAt":"2026-04-23T20:01:39.537Z"}],"details":{"listingId":"01882711-bd41-422e-8f8e-cbb3e286a0f8","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/invoices/4 \\\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, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The x402 challenge for /api/v1/invoices/4 specifies maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base","source_url":"https://lowpaymentfee.com/api/v1/invoices/4"},{"claim":"Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure","source_url":"https://lowpaymentfee.com"},{"claim":"Docs, API, pricing, and README pages contain only a 'Connect wallet' prompt","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management","Fetching real-time financial data such as exchange rates, token quotes, and gas estimates on a per-call basis","Running data analytics queries and exporting data with per-request billing","Using utility services like geocoding, validation, and conversion via micropayments"],"bestFor":["Agents and developers who want keyless, pay-per-use API access","Use cases requiring low-friction micropayments on Base/USDC","Prototyping and low-volume usage where subscription plans are overkill"],"notFor":["High-volume production workloads needing guaranteed SLAs and detailed documentation","Users who need well-documented request/response schemas before integrating","Teams that cannot transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:50.262Z"},"updatedAt":"2026-04-23T20:01:39.537Z"}}