{"id":"f4c3d8fa-1e0b-4b6d-9a43-fbea81529d31","shortId":"6ydNuU","kind":"x402","title":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","tagline":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","description":"lowpaymentfee.com offers a suite of pay-per-request API endpoints gated by the x402 protocol, settling payments in USDC on the Base network. The specific endpoint `/api/v1/keys/20` is listed as \"Premium API Access\" and costs up to $0.02 per call (maxAmountRequired of 20,000 base units of USDC, which is 6-decimal, equaling $0.02). No API keys, subscriptions, or rate limits are advertised — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe broader platform groups its endpoints into 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 listed at the same $0.02/request price point.\n\nThis particular endpoint (`/api/v1/keys/20`) does not have detailed documentation about its request or response schema beyond the x402 challenge. The probe confirms it is live, returning a proper 402 challenge with x402 version 1. The payment is directed to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. The endpoint accepts POST requests and has a payment timeout of 300 seconds.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","premium-api-access","no-api-key-required","post-method"],"categories":["api-gateway","infrastructure"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","lowpaymentfee","Base network API","crypto-gated API","premium access endpoint"],"warnings":["No OpenAPI or schema documentation available for this endpoint","The exact functionality of /api/v1/keys/20 ('Premium API Access') is unclear — it may generate or return API keys, but this is unconfirmed","Crawled /api, /pricing, and /README pages returned no meaningful content beyond 'Connect wallet'","No example request or response bodies are available"],"endpointUrl":"https://lowpaymentfee.com/api/v1/keys/20","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/keys/20","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 via a valid 402 x402 challenge, and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI spec, no request/response schema documentation, no examples, and the purpose of this specific endpoint ('Premium API Access' at /api/v1/keys/20) is vague. The crawled pages beyond the landing page returned only 'Connect wallet' with no useful 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'/request':13,28,159 '0.02':12,27,69,85,158 '000':75 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':202 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':205 '1':195 '20':74 '300':219 '402':190 '6':82 'Base network API' 'USDC micropayment API' 'accept':210 'access':7,22,64 'address':201 'advertis':94 'ai':125 'analysi':129 'analyt':119 'api':6,21,40,63,87 'attach':97 'base':9,24,53,76,207 'base-network' 'beyond':177 'broader':110 'call':4,19,71 'caller':95 'categori':117 'challeng':180,191 'classif':132 'confirm':183 'convers':149 'cost':66 'crypto-gated API' 'data':118,122 'decim':83 'detail':169 'direct':199 'document':170 'embed':133 'endpoint':41,57,114,152,164,209 'equal':84 'estim':143 'exchang':138 'export':123 'feed':137 'financ':134 'four':116 'gas':142 'gate':42 'generat':150 'geocod':147 'group':112 'header':102 'infrastructur':145 'insight':124 'key':88 'learn':127 'limit':92 'list':60,154 'live':186 'lowpaymentfee' 'lowpaymentfee.com':31 'machin':126 'maxamountrequir':72 'metric':120 'network':54 'no-api-key-required' 'offer':32 'particular':163 'pay':2,17,37 'pay-per-cal':1,16 'pay-per-call API' 'pay-per-request':36 'payment':48,101,107,197,216 'per':3,18,38,70 'platform':111 'point':161 'post':211 'post-method' 'premium':5,20,62 'premium access endpoint' 'premium-api-access' 'price':136,160 'probe':182 'proof':108 'proper':189 'protocol':46 'quot':141 'rate':91,139 'report':121 'request':39,173,212 'respons':175 'return':187 'schema':176 'second':220 'sentiment':128 'settl':47 'simpli':96 'specif':56 'subscript':89 'suit':34 'summar':131 'text':130 'timeout':217 'token':140 'unit':77 'usdc':15,30,50,79,204 'usdc-settlement' 'use':203 'util':146 'valid':105,148 'version':194 'via':10,25 'web3':135 'x':100 'x-payment':99 'x402':11,26,45,106,179,193 'x402 API' 'x402-payment'","prices":[{"id":"bfe8948e-deed-4cf8-8bbe-f24ef7aa263c","listingId":"f4c3d8fa-1e0b-4b6d-9a43-fbea81529d31","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/keys/20","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:23.441Z"}],"sources":[{"listingId":"f4c3d8fa-1e0b-4b6d-9a43-fbea81529d31","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/keys/20","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:23.441Z","lastSeenAt":"2026-04-22T01:02:18.756Z"}],"details":{"listingId":"f4c3d8fa-1e0b-4b6d-9a43-fbea81529d31","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/keys/20 \\\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":"Endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/keys/20"},{"claim":"USDC contract address on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/keys/20"},{"claim":"All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Programmatic access to premium API features without managing API keys or subscriptions","Agent-driven workflows that need on-demand, pay-as-you-go API calls settled in USDC","Accessing a broad set of data, AI, finance, and utility endpoints at low per-request cost"],"bestFor":["Developers or agents wanting zero-commitment, per-request API billing","x402-compatible clients on the Base network","Low-cost micropayment API consumption without rate limits"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume consumers who would benefit from bulk pricing or subscriptions","Callers without USDC on Base or without x402 client support"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:05.823Z"},"updatedAt":"2026-04-22T01:02:18.756Z"}}