{"id":"5448e2e1-1409-4377-8bf1-c109075365a1","shortId":"rK3cSg","kind":"x402","title":"Pay-per-call API platform on Base (USDC) via x402 — $0.02/request, no API keys required.","tagline":"Pay-per-call API platform on Base (USDC) via x402 — $0.02/request, no API keys required.","description":"lowpaymentfee.com is a pay-per-request API platform that uses the x402 protocol to accept USDC payments on the Base network. The specific endpoint `/api/v1/payments/321` is listed as \"Premium API Access\" and charges up to 20,000 base units of USDC (i.e., $0.02) per call. The platform advertises no API keys, no rate limits, and instant access — you simply attach an x402 payment header to each request.\n\nThe broader platform offers 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 uniformly priced at $0.02 per request.\n\nThis particular endpoint (`/api/v1/payments/321`) is confirmed live, returning a proper 402 challenge with x402 version 1. The payment is settled on-chain to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. The timeout for payment is 300 seconds. However, documentation is extremely thin — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no additional technical detail, so the actual request/response schemas for this endpoint are unknown.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","no-api-key","premium-api-access","json-response"],"categories":["payments","infrastructure"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","crypto API payments","402 payment protocol"],"warnings":["No API documentation available — docs, pricing, API, and README pages all show only 'Connect wallet'","The purpose and expected input/output of /api/v1/payments/321 ('Premium API Access') is not documented anywhere","No OpenAPI spec or request/response schema provided","The endpoint name 'Premium API Access' is generic and does not describe what the endpoint actually does"],"endpointUrl":"https://lowpaymentfee.com/api/v1/payments/321","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/payments/321","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is confirmed live with a valid 402 challenge and clear pricing ($0.02 USDC on Base). However, there is no OpenAPI schema, no documentation beyond a landing page listing, no request/response examples, and all doc pages render only 'Connect wallet'. The actual functionality behind 'Premium API Access' at /api/v1/payments/321 is 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'/request':13,30 '0.02':12,29,78,150 '000':72 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':178 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':181 '1':168 '20':71 '300':189 '402':163 '402 payment protocol' 'Base network API' 'USDC micropayment API' 'accept':50 'access':66,92 'across':108 'actual':217 'addit':212 'address':177 'advertis':83 'ai':118 'analysi':122 'analyt':112 'api':5,15,22,32,42,65,85,198 'attach':95 'base':8,25,55,73,183 'broader':104 'call':4,21,80 'categori':110 'chain':175 'challeng':164 'charg':68 'classif':125 'confirm':158 'connect':207 'convers':142 'crypto API payments' 'data':111,115 'detail':214 'doc':197 'document':192 'embed':126 'endpoint':59,107,145,155,222 'estim':136 'exchang':131 'export':116 'extrem':194 'feed':130 'financ':127 'four':109 'gas':135 'generat':143 'geocod':140 'header':99 'howev':191 'i.e':77 'infrastructur':138 'insight':117 'instant':91 'json-response' 'key':16,33,86 'learn':120 'limit':89 'list':62 'live':159 'lowpaymentfee' 'lowpaymentfee.com':35 'machin':119 'metric':113 'network':56 'no-api-key' 'offer':106 'on-chain':173 'page':202 'particular':154 'pay':2,19,39 'pay-per-cal':1,18 'pay-per-call API' 'pay-per-request':38 'payment':52,98,170,187 'per':3,20,40,79,151 'platform':6,23,43,82,105 'premium':64 'premium-api-access' 'price':129,148,199 'prompt':209 'proper':162 'protocol':48 'quot':134 'rate':88,132 'readm':201 'render':204 'report':114 'request':41,102,152 'request/response':218 'requir':17,34 'return':160 'schema':219 'second':190 'sentiment':121 'settl':172 'simpli':94 'specif':58 'summar':124 'technic':213 'text':123 'thin':195 'timeout':185 'token':133 'uniform':147 'unit':74 'unknown':224 'usdc':9,26,51,76,180 'usdc-base' 'use':45,179 'util':139 'valid':141 'version':167 'via':10,27 'wallet':208 'web3':128 'x402':11,28,47,97,166 'x402 API' 'x402-payment'","prices":[{"id":"a5b28c90-64ca-42b0-8178-77a2d6be48a9","listingId":"5448e2e1-1409-4377-8bf1-c109075365a1","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/payments/321","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:50:25.328Z"}],"sources":[{"listingId":"5448e2e1-1409-4377-8bf1-c109075365a1","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/payments/321","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:50:25.328Z","lastSeenAt":"2026-04-23T23:02:46.117Z"}],"details":{"listingId":"5448e2e1-1409-4377-8bf1-c109075365a1","quickStartSnippet":"# Send a POST with an x402 payment header (USDC on Base)\ncurl -X POST https://lowpaymentfee.com/api/v1/payments/321 \\\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 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/payments/321"},{"claim":"All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/payments/321"},{"claim":"Platform offers endpoints in Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Agents that need to make authenticated API calls without managing API keys","Programmatic access to premium data or services with per-request crypto payments","Testing x402 protocol integrations with a low-cost live endpoint","Paying for API access directly from a crypto wallet on Base"],"bestFor":["Developers or agents wanting key-free, pay-as-you-go API access","x402 protocol experimentation at low cost ($0.02/call)","Scenarios where traditional API key management is undesirable"],"notFor":["Users who need detailed API documentation or well-defined request/response schemas","High-volume use cases where per-request payment overhead is impractical","Users without access to USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:07.149Z"},"updatedAt":"2026-04-23T23:02:46.117Z"}}