{"id":"ac9119cf-ee69-4945-bbc0-3495000979b2","shortId":"rhzbDc","kind":"x402","title":"Pay-per-request API suite on Base (USDC) covering data, AI, finance, and utility endpoints.","tagline":"Pay-per-request API suite on Base (USDC) covering data, AI, finance, and utility endpoints.","description":"lowpaymentfee.com is an x402-enabled API platform that offers a broad collection of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities. All endpoints are priced at $0.02 per request, paid in USDC on the Base network via the x402 protocol. No API keys, rate limits, or subscriptions are required — callers simply attach an X-PAYMENT header with a valid payment proof to access any endpoint.\n\nThe specific endpoint at `/api/v1/invoices/44` is listed as \"Premium API Access\" and returns a 402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) on Base. The platform also advertises endpoints for sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, token quotes, gas estimates, geocoding, validation, conversion, and generation — all at the same $0.02 price point.\n\nDocumentation is extremely sparse. The docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI schema, no request/response examples, and no description of what each endpoint actually returns. The invoices/44 endpoint in particular has no documented input or output format beyond the x402 challenge metadata indicating it accepts POST requests and returns application/json.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","data-analytics","ai-sentiment","ai-summarization","ai-classification","ai-embeddings","finance-prices","exchange-rates","crypto-quotes","gas-estimates","geocoding","validation","conversion","generation"],"categories":["ai","finance","data","infrastructure"],"synonyms":["low payment fee","x402 api","pay per call api","micropayment api","base usdc api","402 payment api","lowpaymentfee"],"warnings":["Documentation pages (docs, API, pricing, README) are all empty — only showing 'Connect wallet'","No OpenAPI or schema available for any endpoint","The specific endpoint /api/v1/invoices/44 has no documented purpose, input format, or response structure","The broader platform lists 16+ endpoints but none have documented request/response contracts","Cannot verify that any of the advertised AI, finance, or utility endpoints actually function as described"],"endpointUrl":"https://lowpaymentfee.com/api/v1/invoices/44","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/44","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, confirming it accepts payments. However, documentation is essentially nonexistent — all doc pages show only 'Connect wallet' with no content. There is no OpenAPI schema, no request/response examples, and the specific purpose of /api/v1/invoices/44 is unclear beyond the generic 'Premium API Access' label. The broader platform lists many endpoints but provides no detail on inputs or 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'list':109 'low payment fee' 'lowpaymentfee' 'lowpaymentfee.com':33 'metadata':219 'micropayment api' 'network':72 'offer':42 'openapi':189 'output':213 'page':174 'paid':66 'particular':207 'pay':2,18 'pay per call api' 'pay-per-request':1,17 'payment':92,97 'per':3,19,64 'platform':40,133 'point':163 'post':223 'premium':111 'price':61,144,162,171 'prompt':181 'proof':98 'protocol':76 'quot':149 'rate':80,147 'readm':173 'render':176 'request':4,20,65,119,224 'request/response':192 'requir':85 'return':115,202,226 'schema':190 'sentiment':138 'simpli':87 'span':48 'spars':167 'specif':104 'subscript':83 'suit':6,22 'summar':141 'text':140 'token':148 'unit':125 'usdc':9,25,68,127 'usdc-base' 'util':15,31,57 'valid':96,153 'validation' 'via':73 'wallet':180 'x':91 'x-payment':90 'x402':37,75,217 'x402 api' 'x402-enabled':36 'x402-payment'","prices":[{"id":"9e5b5881-04ea-48db-8868-9b10e7635ded","listingId":"ac9119cf-ee69-4945-bbc0-3495000979b2","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/44","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:38:29.740Z"}],"sources":[{"listingId":"ac9119cf-ee69-4945-bbc0-3495000979b2","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/invoices/44","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:38:29.740Z","lastSeenAt":"2026-04-22T19:30:51.362Z"}],"details":{"listingId":"ac9119cf-ee69-4945-bbc0-3495000979b2","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/invoices/44 \\\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":"All endpoints priced at $0.02 per request with no API keys, rate limits, or minimums","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":"x402 challenge for /api/v1/invoices/44 requests maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/invoices/44"},{"claim":"Payment asset is USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base network","source_url":"https://lowpaymentfee.com/api/v1/invoices/44"},{"claim":"Docs, API, pricing, and README pages render only 'Connect wallet' with no further content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Accessing AI inference (sentiment, summarization, classification, embeddings) on a per-request payment basis","Fetching real-time crypto token quotes, gas estimates, and exchange rates without an API key","Running geocoding, data validation, or format conversion as one-off paid utility calls","Exporting analytics data or generating insights reports via pay-as-you-go endpoints"],"bestFor":["Agents or developers who want keyless, pay-per-call API access settled on-chain","Low-volume or sporadic usage where subscriptions are wasteful","Web3-native applications that can attach x402 payment headers natively"],"notFor":["High-volume production workloads needing guaranteed SLAs and detailed documentation","Users who need well-documented request/response schemas before integrating","Anyone without access to USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:41.722Z"},"updatedAt":"2026-04-22T19:30:51.362Z"}}