{"id":"9df6ae16-0e7a-4494-9a30-1d91adffc45c","shortId":"9Em3Uf","kind":"x402","title":"Pay-per-call API platform on Base network — $0.02/request via x402 USDC payments.","tagline":"Pay-per-call API platform on Base network — $0.02/request via x402 USDC payments.","description":"lowpaymentfee.com is a pay-per-request API platform that gates access to a collection of endpoints behind x402 micropayments settled in USDC on the Base network. The specific endpoint `/api/v1/inbox/16` is listed as \"Premium API Access\" and accepts POST requests with a maximum cost of 20,000 base units of USDC (i.e., $0.02 per call, since USDC uses 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an x402 payment header to each request.\n\nThe broader platform advertises four categories of APIs: 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 listed endpoints share the same $0.02/request pricing. However, the specific functionality behind `/api/v1/inbox/16` is not documented beyond the label \"Premium API Access,\" so its exact input/output behavior is unclear.\n\nPayments are made to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the USDC contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` on Base. The x402 challenge specifies a 300-second payment timeout and returns `application/json` responses.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","json-api","post-method","no-api-key","micropayment"],"categories":["api-gateway","infrastructure"],"synonyms":["low payment fee","x402 api","micropayment api","pay per call api","base network api","usdc api access","402 payment api"],"warnings":["No documentation exists for the specific endpoint /api/v1/inbox/16 — its functionality is unknown beyond the label 'Premium API Access'","No OpenAPI or request/response schema is available for any endpoint on the platform","The /api, /pricing, and /README pages returned no meaningful content (only 'Connect wallet')","The broad category labels (AI, Finance, etc.) on the homepage cannot be verified as functional"],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/16","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/inbox/16","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no documentation of what /api/v1/inbox/16 actually does, no request/response schema, no OpenAPI spec, and the crawled pages beyond the homepage returned only 'Connect wallet' with no useful content. The endpoint's purpose is essentially 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'/request':11,26,160 '0.02':10,25,84,159 '000':78 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':189 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':194 '20':77 '300':202 '402 payment api' '6':90 'accept':69 'access':42,67,176 'address':188 'advertis':115 'ai':127 'analysi':131 'analyt':121 'api':5,20,38,66,93,119,175 'application/json':208 'attach':104 'base':8,23,56,79,196 'base network api' 'behavior':181 'behind':48,166 'beyond':171 'broader':113 'call':4,19,86 'caller':102 'categori':117 'challeng':199 'classif':134 'collect':45 'commit':99 'contract':193 'convers':151 'cost':75 'data':120,124 'decim':91 'document':170 'embed':135 'endpoint':47,60,155 'estim':145 'exact':179 'exchang':140 'export':125 'feed':139 'financ':136 'four':116 'function':165 'gas':144 'gate':41 'generat':152 'geocod':149 'header':108 'howev':162 'i.e':83 'infrastructur':147 'input/output':180 'insight':126 'json-api' 'key':94 'label':173 'learn':129 'limit':96 'list':63,154 'low payment fee' 'lowpaymentfee.com':31 'machin':128 'made':186 'maximum':74 'metric':122 'micropay':50 'micropayment' 'micropayment api' 'network':9,24,57 'no-api-key' 'pay':2,17,35 'pay per call api' 'pay-per-cal':1,16 'pay-per-request':34 'payment':15,30,107,184,204 'per':3,18,36,85 'platform':6,21,39,114 'post':70 'post-method' 'premium':65,174 'price':138,161 'quot':143 'rate':95,141 'report':123 'request':37,71,111 'requir':101 'respons':209 'return':207 'second':203 'sentiment':130 'settl':51 'share':156 'simpli':103 'sinc':87 'specif':59,164 'specifi':200 'summar':133 'text':132 'timeout':205 'token':142 'unclear':183 'unit':80 'upfront':98 'usdc':14,29,53,82,88,192 'usdc api access' 'usdc-base' 'use':89,190 'util':148 'valid':150 'via':12,27 'web3':137 'x402':13,28,49,106,198 'x402 api' 'x402-payment'","prices":[{"id":"e831d12c-1f91-48b1-b658-a9e32415b6fb","listingId":"9df6ae16-0e7a-4494-9a30-1d91adffc45c","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/inbox/16","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:21.731Z"}],"sources":[{"listingId":"9df6ae16-0e7a-4494-9a30-1d91adffc45c","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/16","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:21.731Z","lastSeenAt":"2026-04-22T01:02:16.502Z"}],"details":{"listingId":"9df6ae16-0e7a-4494-9a30-1d91adffc45c","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/16 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-token>\" \\\n  -d '{}'","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/inbox/16"},{"claim":"All listed endpoints are priced at $0.02 per request with no API keys, rate limits, or minimums","source_url":"https://lowpaymentfee.com"},{"claim":"The platform advertises APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"USDC contract address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/inbox/16"}],"useCases":["Accessing premium API endpoints without API key registration","Making micropayment-gated API calls from autonomous agents","Paying per request for data or utility services on Base network"],"bestFor":["Agents or developers wanting zero-signup API access","Micropayment use cases where $0.02/call is cost-effective","x402-compatible clients on the Base L2 network"],"notFor":["Users who need detailed documentation or OpenAPI specs before integrating","High-volume callers who would benefit from bulk pricing or subscriptions","Callers who cannot settle payments in USDC on Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:08.388Z"},"updatedAt":"2026-04-22T01:02:16.502Z"}}