{"id":"75874e59-fe47-4ae3-96b2-8f0315361c23","shortId":"7qGvYz","kind":"x402","title":"x402-gated API suite: analytics, AI, finance, and utilities at $0.02/request on Base.","tagline":"x402-gated API suite: analytics, AI, finance, and utilities at $0.02/request on Base.","description":"lowpaymentfee.com is a multi-category API platform that gates every endpoint behind the x402 payment protocol, settling in USDC on the Base network. The specific endpoint `/api/v1/cards/4` 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 or rate limits are advertised; callers simply attach an X-PAYMENT header to pay per request.\n\nThe broader platform offers 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 listed at the same $0.02/request price point.\n\nDocumentation is extremely sparse — the /docs, /pricing, /api, 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 crawled material. The x402 challenge for this specific endpoint is live and well-formed, but without documentation it is unclear what request body `/api/v1/cards/4` expects or what it returns.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","per-request-pricing","no-api-key","post-endpoint","json-response"],"categories":["api-gateway","misc"],"synonyms":["low payment fee","x402 API","pay-per-call API","USDC API","Base network API","micropayment API","premium API access"],"warnings":["No documentation available — /docs, /pricing, /api, and /README all return only 'Connect wallet' with no content","No OpenAPI spec or request/response schema provided","The purpose of /api/v1/cards/4 ('Premium API Access') is completely undocumented — unclear what data or service it provides","All non-root pages appear to be empty wallet-connect shells"],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/4","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/cards/4","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The x402 challenge is live and well-formed, confirming the endpoint exists and accepts payment. However, there is zero documentation on what this specific endpoint does, what request body it expects, or what it returns. The /docs and other pages are empty beyond a wallet-connect prompt. The listing is effectively a stub with confirmed 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'/api/v1/cards/4':58,224 '/docs':166 '/pricing':167 '/readme':170 '/request':13,28,158 '0.02':12,27,81,157 '000':75 '20':74 '6':87 'Base network API' 'USDC API' 'accept':66 'access':64 'across':114 'advertis':96 'ai':7,22,124 'analysi':128 'analyt':6,21,118 'api':4,19,37,63,90 'attach':99 'avail':197 'base':15,30,53,76 'base-network' 'behind':43 'bodi':223 'broader':110 'call':83 'caller':97 'categori':36,116 'challeng':204 'classif':131 'connect':176 'convers':148 'cost':72 'crawl':200 'data':117,121 'decim':88 'detail':183 'document':161,192,217 'embed':132 'endpoint':42,57,113,151,208 'estim':142 'everi':41 'exampl':196 'exchang':137 'expect':225 'export':122 'extrem':163 'feed':136 'financ':8,23,133 'form':214 'four':115 'gas':141 'gate':3,18,40 'generat':149 'geocod':146 'header':104 'i.e':80 'infrastructur':144 'insight':123 'json-response' 'key':91 'learn':126 'limit':94 'list':60,153 'live':210 'low payment fee' 'lowpaymentfee.com':31 'machin':125 'materi':201 'maximum':71 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'x402-payment'","prices":[{"id":"50dc7388-b23d-43e8-9068-62f4a519e2da","listingId":"75874e59-fe47-4ae3-96b2-8f0315361c23","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/cards/4","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:32.206Z"}],"sources":[{"listingId":"75874e59-fe47-4ae3-96b2-8f0315361c23","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/4","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:32.206Z","lastSeenAt":"2026-04-22T10:31:28.561Z"}],"details":{"listingId":"75874e59-fe47-4ae3-96b2-8f0315361c23","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/cards/4 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-token>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/cards/4"},{"claim":"All 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/cards/4"}],"useCases":["Agents that need on-demand API access without pre-registration or API keys","Programmatic access to a bundled set of analytics, AI, finance, and utility endpoints","Demonstrating or testing x402 payment protocol integrations"],"bestFor":["Developers exploring x402 payment-gated APIs","Agents needing keyless, pay-per-request access on Base","Low-volume callers who want no subscription commitment"],"notFor":["Production workloads requiring documented request/response schemas","Users who need detailed API documentation or SDKs","High-volume use cases where $0.02/request adds up without volume discounts"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:26.979Z"},"updatedAt":"2026-04-22T10:31:28.561Z"}}