{"id":"20be135d-ca31-483e-9528-d17b2e0f7375","shortId":"sgpYfs","kind":"x402","title":"Pay-per-call API platform on Base via x402 — $0.02/request, no API keys required.","tagline":"Pay-per-call API platform on Base via x402 — $0.02/request, no API keys required.","description":"lowpaymentfee.com is an x402-enabled API marketplace that offers a broad set of endpoints across data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. Every endpoint costs $0.02 per request, paid in USDC on the Base network via the x402 protocol. There are no API keys, no rate limits, and no subscriptions — callers simply attach an x402 payment header to each request.\n\nThe specific endpoint at `/api/v1/transactions/139` is listed as \"Premium API Access\" and accepts POST requests. Its x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is sent to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout.\n\nThe site advertises additional endpoint categories including 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. However, documentation is extremely sparse: the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The actual functionality behind this specific `/transactions/139` endpoint is unclear from the available material.","tags":[],"capabilities":["x402-payment","pay-per-request","usdc-base","no-api-key","post-endpoint","json-response"],"categories":["api-marketplace","infrastructure"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","low payment fee API","402 payment API"],"warnings":["No OpenAPI spec or schema documentation available","The actual functionality behind /api/v1/transactions/139 is undocumented — 'Premium API Access' is the only description","All documentation pages (docs, API, pricing, README) render only 'Connect wallet' with no technical content","No request body schema or response schema is documented anywhere","The broad claims of AI, analytics, finance, and utility endpoints cannot be verified from available material"],"endpointUrl":"https://lowpaymentfee.com/api/v1/transactions/139","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/transactions/139","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 x402 402 challenge, confirming it accepts payments. However, there is no documentation, no OpenAPI spec, no request/response examples, and the actual functionality of this specific endpoint (/api/v1/transactions/139) is entirely unclear. The docs, pricing, and README pages are all empty beyond a wallet-connect 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'/request':12,28 '/transactions/139':223 '0.02':11,27,60,129,176 '000':118 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':140 '0x8335':123 '20':117 '2913':124 '300':143 '402 payment API' '6':133 'Base network API' 'USDC micropayment API' 'accept':107 'access':105 'across':48 'actual':218 'addit':149 'address':139 'advertis':113,148 'ai/ml':51 'analysi':154 'analyt':50 'api':5,14,21,30,39,77,104,186 'attach':87 'avail':216,229 'base':8,24,68,119,126 'behind':220 'broad':44 'call':4,20 'caller':85 'categori':151 'challeng':112 'classif':157 'connect':195 'convers':169 'cost':59 'data':49 'decim':134 'detail':202 'doc':185 'document':180,211 'embed':158 'enabl':38 'endpoint':47,58,97,150,224 'equal':128 'estim':166 'everi':57 'exampl':214 'exchang':161 'extrem':182 'feed':160 'finance/web3':53 'function':219 'gas':165 'generat':171 'geocod':167 'given':130 'header':91 'howev':179 'includ':152 'infer':52 'infrastructur':55 'json-response' 'key':15,31,78 'limit':81 'list':101 'low payment fee API' 'lowpaymentfee' 'lowpaymentfee.com':33 'marketplac':40 'materi':230 'maxamountrequir':115 'network':69 'no-api-key' 'offer':42 'openapi':206 'page':190 'paid':63 'pay':2,18 'pay-per-cal':1,17 'pay-per-call API' 'pay-per-request' 'payload':215 'payment':90,135 'per':3,19,61 'platform':6,22 'point':178 'post':108 'post-endpoint' 'premium':103 'price':159,177,187 'prompt':197 'protocol':73 'quot':164 'rate':80,162 'readm':189 'render':192 'request':62,94,109 'request/response':209 'requir':16,32 'schema':210 'second':144 'sent':137 'sentiment':153 'set':45 'simpli':86 'site':147 'spars':183 'spec':207 'specif':96,222 'subscript':84 'summar':156 'technic':201 'text':155 'timeout':145 'token':163 'unclear':226 'unit':120 'usdc':65,122,131 'usdc-base' 'util':56 'valid':168 'via':9,25,70 'wallet':196 'x402':10,26,37,72,89,111 'x402 API' 'x402-enabled':36 'x402-payment'","prices":[{"id":"6cd87d9b-67a0-48b0-82e0-255d0490eb3f","listingId":"20be135d-ca31-483e-9528-d17b2e0f7375","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/transactions/139","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:58:28.553Z"}],"sources":[{"listingId":"20be135d-ca31-483e-9528-d17b2e0f7375","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/transactions/139","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:58:28.553Z","lastSeenAt":"2026-04-22T17:02:12.059Z"}],"details":{"listingId":"20be135d-ca31-483e-9528-d17b2e0f7375","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/transactions/139 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-header>\"","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/transactions/139"},{"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":"The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/transactions/139"},{"claim":"The site advertises endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Accessing pay-per-call API services without managing API keys or subscriptions","Making micropayment-gated API calls settled in USDC on Base","Integrating x402-compatible endpoints into agent workflows"],"bestFor":["Developers wanting zero-commitment, pay-as-you-go API access","AI agents that can settle x402 payments autonomously","Users who prefer crypto-native micropayments over subscription billing"],"notFor":["Users needing detailed API documentation or OpenAPI specs before integrating","Applications requiring guaranteed SLAs or enterprise support","Users without access to USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:43.993Z"},"updatedAt":"2026-04-22T17:02:12.059Z"}}