{"id":"9565d0b3-3218-49bd-bfcc-b84de689378e","shortId":"w8gU4k","kind":"x402","title":"x402-payable API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.","tagline":"x402-payable API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.","description":"lowpaymentfee.com is an x402-enabled API platform that exposes a broad set of 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 priced at $0.02 per request, payable in USDC on the Base network via the x402 protocol — no API keys, no rate limits, and no signup required.\n\nThe specific endpoint at `/api/v1/carts/21` is listed as \"Premium API Access\" and returns a valid x402 challenge with a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the `exact` scheme to the specified payTo address, with a 300-second timeout. The endpoint accepts HTTP POST requests and returns `application/json`.\n\nDocumentation beyond the landing page is extremely sparse — the /docs, /api, /pricing, and /README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available. The purpose of the `/api/v1/carts/21` endpoint specifically is unclear; it does not correspond to any of the advertised API categories on the homepage. Prospective users should be aware that the actual functionality behind this endpoint is undocumented.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","data-analytics","ai-inference","sentiment-analysis","text-summarization","classification","embeddings","finance-data","geocoding","no-api-key"],"categories":["ai","finance","data","infrastructure"],"synonyms":["low payment fee","x402 api","pay-per-call api","micropayment api","base network api","usdc api","402 payment api"],"warnings":["The /api/v1/carts/21 endpoint does not match any of the advertised API paths on the homepage — its actual functionality is unknown.","All documentation pages (/docs, /api, /pricing, /README) render only 'Connect wallet' with no usable content.","No OpenAPI spec, no request/response schema, and no usage examples are available.","The platform lists many endpoints on its homepage but none have documented input/output schemas."],"endpointUrl":"https://lowpaymentfee.com/api/v1/carts/21","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/carts/21","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live and returns a valid x402 402 challenge, confirming pricing and payment details. However, documentation is essentially nonexistent beyond the landing page listing. The specific /api/v1/carts/21 endpoint is not described among the advertised APIs, there is no OpenAPI spec, no request/response schema, and no examples. This is effectively a stub 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'/api/v1/carts/21':119,224 '/docs':189 '/pricing':191 '/readme':193 '/request':17,34 '0.02':16,33,91,148 '000':137 '0x8335':142 '20':136 '2913':143 '300':168 '402 payment api' '6':152 'accept':173 'access':125 'across':50 'actual':250 'address':165 'advertis':237 'ai':10,27,60 'ai-inference' 'analysi':64 'analyt':54 'api':4,21,41,106,124,238 'application/json':179 'avail':219 'awar':247 'base':7,24,99,138,145 'base network api' 'behind':252 'beyond':181 'broad':46 'categori':52,239 'challeng':131 'classif':67 'classification' 'connect':199 'content':205 'convers':84 'correspond':232 'data':9,26,53,57 'data-analytics' 'decim':153 'document':180,214 'embed':68 'embeddings' 'enabl':40 'endpoint':14,31,49,87,117,172,225,254 'equal':147 'estim':78 'exact':159 'exampl':218 'exchang':73 'export':58 'expos':44 'extrem':186 'feed':72 'financ':11,28,69 'finance-data' 'four':51 'function':251 'gas':77 'generat':85 'geocod':82 'geocoding' 'given':149 'homepag':242 'http':174 'infrastructur':80 'insight':59 'key':107 'land':183 'learn':62 'limit':110 'list':121 'low payment fee' 'lowpaymentfee.com':35 'machin':61 'made':156 'maxamountrequir':134 'metric':55 'micropayment api' 'network':100 'no-api-key' 'offer':8,25 'openapi':209 'page':184,194 'pay-per-call api' 'pay-per-request' 'payabl':3,20,94 'payment':154 'payto':164 'per':92 'platform':5,22,42 'post':175 'premium':123 'price':71,89 'prompt':201 'prospect':243 'protocol':104 'purpos':221 'quot':76 'rate':74,109 'render':196 'report':56 'request':93,176 'request/response':212 'requir':114 'return':127,178 'schema':213 'scheme':160 'second':169 'sentiment':63 'sentiment-analysis' 'set':47 'signup':113 'spars':187 'spec':210 'specif':116,226 'specifi':163 'summar':66 'text':65 'text-summarization' 'timeout':170 'token':75 'unclear':228 'undocu':256 'unit':139 'usag':217 'usdc':96,141,150 'usdc api' 'usdc-base' 'user':244 'util':13,30,81 'valid':83,129 'via':101,157 'wallet':200 'web3':70 'x402':2,19,39,103,130 'x402 api' 'x402-enabled':38 'x402-payable':1,18 'x402-payment'","prices":[{"id":"d432bc82-7ed9-4106-8de2-359fbb6d282a","listingId":"9565d0b3-3218-49bd-bfcc-b84de689378e","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/carts/21","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:38:35.153Z"}],"sources":[{"listingId":"9565d0b3-3218-49bd-bfcc-b84de689378e","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/carts/21","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:38:35.153Z","lastSeenAt":"2026-04-22T20:00:44.200Z"}],"details":{"listingId":"9565d0b3-3218-49bd-bfcc-b84de689378e","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/carts/21 \\\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":"All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"The x402 challenge for /api/v1/carts/21 specifies maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base with a 300-second timeout.","source_url":"https://lowpaymentfee.com/api/v1/carts/21"},{"claim":"Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure.","source_url":"https://lowpaymentfee.com"},{"claim":"Documentation pages /docs, /api, /pricing, /README all show only 'Connect wallet' with no further content.","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Agent-driven data retrieval with per-call USDC micropayments","On-demand AI inference (sentiment, summarization, classification) without API key management","Fetching real-time crypto gas estimates or token quotes via x402","Geocoding or data conversion as a utility service with no subscription"],"bestFor":["Developers or agents wanting zero-signup, pay-per-use API access","x402-compatible agents that can settle USDC on Base","Prototyping workflows that need cheap, frictionless API calls"],"notFor":["Users who need detailed API documentation or guaranteed SLAs","High-volume production workloads requiring rate-limit guarantees or bulk pricing","Users without a Base-compatible USDC wallet"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:41.421Z"},"updatedAt":"2026-04-22T20:00:44.200Z"}}