{"id":"9f97f3cd-671a-41d8-a3d7-01c89d6a9910","shortId":"dXZFGm","kind":"x402","title":"x402-gated API suite on Base: analytics, AI, finance, and utility endpoints at $0.02/request via USDC.","tagline":"x402-gated API suite on Base: analytics, AI, finance, and utility endpoints at $0.02/request via USDC.","description":"lowpaymentfee.com hosts a collection of x402-protocol pay-per-call API endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/carts/58` is listed as \"Premium API Access\" and returns a standard x402 challenge requiring up to 20,000 base-unit USDC (i.e., $0.02) per request. No API keys or rate limits are advertised; callers simply attach an X-PAYMENT header with a valid payment proof.\n\nThe broader platform advertises four endpoint 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 listed endpoints share the same $0.02/request pricing. The x402 challenge confirms settlement via the USDC contract on Base (0x8335…2913) with a 300-second payment timeout.\n\nDocumentation beyond the landing page is extremely thin — 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 usage examples available from the crawl. The `/api/v1/carts/58` path name suggests a shopping-cart or catalog resource, but the actual payload format is undocumented. Agents should expect to experiment or rely on the generic x402 flow (POST with payment header, receive JSON response).","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","data-analytics","ai-inference","sentiment-analysis","text-summarization","classification","embeddings","finance-data","geocoding","no-api-key"],"categories":["api-marketplace","llm","finance","geo"],"synonyms":["lowpaymentfee","low payment fee API","x402 API marketplace","pay-per-call API","USDC micropayment API","Base network API","micro-transaction API"],"warnings":["No OpenAPI or schema documentation available — all doc/pricing/README pages return only 'Connect wallet'","The endpoint path '/api/v1/carts/58' is undocumented; actual request body format and response structure are unknown","The broader platform lists many endpoints but none have documented schemas or examples","Cannot verify that any of the advertised AI, finance, or utility endpoints actually function beyond returning 402 challenges"],"endpointUrl":"https://lowpaymentfee.com/api/v1/carts/58","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/58","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is essentially no documentation: no OpenAPI spec, no request/response schemas, no usage examples, and all doc pages render only 'Connect wallet'. The specific resource path '/api/v1/carts/58' is unexplained. This is effectively a stub 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'/api/v1/carts/58':62,222 '/docs':186 '/pricing':188 '/readme':190 '/request':16,34,156 '0.02':15,33,85,155 '000':79 '0x8335':169 '20':78 '2913':170 '300':173 'Base network API' 'USDC micropayment API' 'access':68 'actual':235 'advertis':95,112 'agent':240 'ai':9,27,123 'ai-inference' 'analysi':127 'analyt':8,26,117 'api':4,22,49,67,89 'attach':98 'avail':217 'base':7,25,56,81,168 'base-network' 'base-unit':80 'beyond':178 'broader':110 'call':48 'caller':96 'cart':229 'catalog':231 'categori':115 'challeng':74,160 'classif':130 'classification' 'collect':40 'confirm':161 'connect':196 'contract':166 'convers':147 'crawl':220 'data':116,120 'data-analytics' 'detail':203 'document':177,212 'embed':131 'embeddings' 'endpoint':13,31,50,60,114,151 'estim':141 'exampl':216 'exchang':136 'expect':242 'experi':244 'export':121 'extrem':183 'feed':135 'financ':10,28,132 'finance-data' 'flow':251 'format':237 'four':113 'gas':140 'gate':3,21 'generat':148 'generic':249 'geocod':145 'geocoding' 'header':103,255 'host':38 'i.e':84 'infrastructur':143 'insight':122 'json':257 'key':90 'land':180 'learn':125 'limit':93 'list':64,150 'low payment fee API' 'lowpaymentfee' 'lowpaymentfee.com':37 'machin':124 'metric':118 'micro-transaction API' 'name':224 'network':57 'no-api-key' 'openapi':207 'page':181,191 'path':223 'pay':46 'pay-per-cal':45 'pay-per-call API' 'pay-per-request' 'payload':236 'payment':102,107,175,254 'per':47,86 'platform':111 'post':252 'premium':66 'price':134,157 'prompt':198 'proof':108 'protocol':44 'quot':139 'rate':92,137 'receiv':256 'reli':246 'render':193 'report':119 'request':87 'request/response':210 'requir':75 'resourc':232 'respons':258 'return':70 'schema':211 'second':174 'sentiment':126 'sentiment-analysis' 'settl':51 'settlement':162 'share':152 'shop':228 'shopping-cart':227 'simpli':97 'spec':208 'specif':59 'standard':72 'suggest':225 'suit':5,23 'summar':129 'technic':202 'text':128 'text-summarization' 'thin':184 'timeout':176 'token':138 'undocu':239 'unit':82 'usag':215 'usdc':18,36,53,83,165 'usdc-settlement' 'util':12,30,144 'valid':106,146 'via':17,35,163 'wallet':197 'web3':133 'x':101 'x-payment':100 'x402':2,20,43,73,159,250 'x402 API marketplace' 'x402-gated':1,19 'x402-payment' 'x402-protocol':42","prices":[{"id":"540eaa4b-3084-496b-85ee-4b31e70e9322","listingId":"9f97f3cd-671a-41d8-a3d7-01c89d6a9910","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/58","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:38:28.553Z"}],"sources":[{"listingId":"9f97f3cd-671a-41d8-a3d7-01c89d6a9910","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/carts/58","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:38:28.553Z","lastSeenAt":"2026-04-23T10:30:30.282Z"}],"details":{"listingId":"9f97f3cd-671a-41d8-a3d7-01c89d6a9910","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/carts/58 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\" \\\n  -d '{}'","exampleRequest":{"url":"https://lowpaymentfee.com/api/v1/carts/58","body":{},"method":"POST","headers":{"X-PAYMENT":"<x402-payment-proof>","Content-Type":"application/json"}},"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base-unit USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/carts/58"},{"claim":"All listed endpoints are priced at $0.02/request with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/carts/58"}],"useCases":["Paying per-call for AI inference (sentiment, summarization, classification, embeddings) without managing API keys","Fetching real-time financial data (prices, exchange rates, gas estimates) via micropayment","Running geocoding or data validation as a utility service with no subscription commitment","Exporting analytics data or generating insights on demand"],"bestFor":["Agents or developers who want zero-signup, pay-as-you-go API access","x402-compatible wallets and agent frameworks on Base","Low-volume or bursty workloads where $0.02/request is cost-effective"],"notFor":["High-volume production workloads needing SLAs, rate-limit guarantees, or detailed documentation","Users without a Base-network USDC wallet or x402-compatible client","Anyone needing well-documented request/response schemas before integration"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:41.83Z"},"updatedAt":"2026-04-23T10:30:30.282Z"}}