{"id":"48d4df49-8111-4682-8f2a-39c05718c58b","shortId":"KvV4v5","kind":"x402","title":"x402-gated premium API endpoint on Base, pay-per-request with USDC.","tagline":"x402-gated premium API endpoint on Base, pay-per-request with USDC.","description":"This endpoint at `/api/endpoint-4` is part of the lowpaymentfee.com platform, which offers a collection of x402-protocol pay-per-request APIs spanning data & analytics, AI/ML inference, finance & Web3 data, and infrastructure utilities. The endpoint is labeled \"Premium API Access\" and accepts POST requests, returning application/json responses. Payment is handled via the x402 exact scheme on the Base network using USDC (asset 0x8335…2913), with a maximum amount of 20,000 units (likely 0.02 USDC given the 6-decimal USDC standard, consistent with the site's advertised $0.02/request pricing).\n\nThe platform advertises no API keys, no rate limits, and instant access — payment is the only gate. However, the specific functionality behind `/api/endpoint-4` is not documented on the site's landing page, which lists endpoints under `/api/v1/` and `/api/v2/` paths but does not mention `/api/endpoint-4`. The docs, pricing, and README pages returned only a \"Connect wallet\" prompt with no substantive content. Without documentation or an output schema describing what this endpoint actually does, its concrete capabilities remain unknown. It is live and responds with a valid 402 challenge, but prospective callers should be aware that the purpose and expected input/output format are undocumented.","tags":[],"capabilities":["x402-payment","usdc-payment","base-network","pay-per-request","post-endpoint","json-response"],"categories":["api","payments"],"synonyms":["premium API","x402 endpoint","USDC API","pay-per-call API","lowpaymentfee","Base network API","micropayment API"],"warnings":["The endpoint /api/endpoint-4 is not listed among the documented APIs on the site's landing page — its purpose is unknown.","All documentation pages (docs, pricing, README) returned only 'Connect wallet' with no substantive content.","No input schema or output schema is provided beyond the generic x402 challenge metadata.","The actual functionality behind this endpoint cannot be verified without making a paid request."],"endpointUrl":"https://lowpaymentfee.com/api/endpoint-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/endpoint-4","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live and returns a valid 402 challenge, but the specific functionality of /api/endpoint-4 is completely undocumented. The site's landing page lists many other endpoints but not this one. Docs, pricing, and README pages are empty beyond a wallet-connect prompt. No input/output schema, no examples, and no description of what the endpoint actually 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'/api/v1':156 '/api/v2':158 '/request':118 '0.02':103,117 '000':100 '0x8335':92 '20':99 '2913':93 '402':206 '6':107 'Base network API' 'USDC API' 'accept':71 'access':69,131 'actual':191 'advertis':116,122 'ai/ml':55 'amount':97 'analyt':54 'api':5,19,51,68,124 'application/json':75 'asset':91 'awar':213 'base':8,22,87 'base-network' 'behind':141 'caller':210 'capabl':195 'challeng':207 'collect':42 'concret':194 'connect':174 'consist':111 'content':180 'data':53,59 'decim':108 'describ':187 'doc':166 'document':145,182 'endpoint':6,20,30,64,154,190 'exact':83 'expect':218 'financ':57 'format':220 'function':140 'gate':3,17,136 'given':105 'handl':79 'howev':137 'infer':56 'infrastructur':61 'input/output':219 'instant':130 'json-response' 'key':125 'label':66 'land':150 'like':102 'limit':128 'list':153 'live':200 'lowpaymentfee' 'lowpaymentfee.com':37 'maximum':96 'mention':163 'micropayment API' 'network':88 'offer':40 'output':185 'page':151,170 'part':34 'path':159 'pay':10,24,48 'pay-per-call API' 'pay-per-request':9,23,47 'payment':77,132 'per':11,25,49 'platform':38,121 'post':72 'post-endpoint' 'premium':4,18,67 'premium API' 'price':119,167 'prompt':176 'prospect':209 'protocol':46 'purpos':216 'rate':127 'readm':169 'remain':196 'request':12,26,50,73 'respond':202 'respons':76 'return':74,171 'schema':186 'scheme':84 'site':114,148 'span':52 'specif':139 'standard':110 'substant':179 'undocu':222 'unit':101 'unknown':197 'usdc':14,28,90,104,109 'usdc-payment' 'use':89 'util':62 'valid':205 'via':80 'wallet':175 'web3':58 'without':181 'x402':2,16,45,82 'x402 endpoint' 'x402-gated':1,15 'x402-payment' 'x402-protocol':44","prices":[{"id":"1b203805-9897-4acc-a72c-e648d328cfcd","listingId":"48d4df49-8111-4682-8f2a-39c05718c58b","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/endpoint-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":"2026-04-18T18:31:54.824Z"}],"sources":[{"listingId":"48d4df49-8111-4682-8f2a-39c05718c58b","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/endpoint-4","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:31:54.824Z","lastSeenAt":"2026-04-23T05:00:37.164Z"}],"details":{"listingId":"48d4df49-8111-4682-8f2a-39c05718c58b","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/endpoint-4\n# Returns 402 with X-PAYMENT challenge; attach a valid x402 payment header to proceed.","exampleRequest":null,"exampleResponse":{"error":"X-PAYMENT header is required","accepts":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","scheme":"exact","network":"base","mimeType":"application/json","resource":"https://lowpaymentfee.com/api/endpoint-4","description":"Premium API Access","maxAmountRequired":"20000","maxTimeoutSeconds":300}],"x402Version":1},"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The site advertises $0.02/request pricing with no API keys, no rate limits, and instant access on the Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"The 402 challenge specifies USDC on Base with maxAmountRequired of 20000 and payTo address 0x1A2B…85F3.","source_url":"https://lowpaymentfee.com/api/endpoint-4"},{"claim":"The site lists endpoints under /api/v1/ and /api/v2/ paths but does not list /api/endpoint-4.","source_url":"https://lowpaymentfee.com"}],"useCases":["Programmatic access to an undocumented premium API service via x402 micropayment","Agent-driven pay-per-request API consumption without API keys","Demonstrating x402 payment protocol integration on the Base network"],"bestFor":["Developers experimenting with x402 payment-gated APIs","Agents that can handle x402 challenges and USDC payments on Base","Users who want keyless, pay-as-you-go API access"],"notFor":["Anyone needing documented input/output contracts before calling","Use cases requiring guaranteed SLAs or support","Users without access to USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:15:01.268Z"},"updatedAt":"2026-04-23T05:00:37.164Z"}}