{"id":"44ddfb10-df91-45bf-a71a-5a8549bdc639","shortId":"h5Lmgc","kind":"x402","title":"Pay-per-request API suite on Base (USDC) — data, AI, finance, and utility endpoints at $0.02/call.","tagline":"Pay-per-request API suite on Base (USDC) — data, AI, finance, and utility endpoints at $0.02/call.","description":"lowpaymentfee.com hosts a collection of x402-enabled API endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/inbox/12` is labeled \"Premium API Access\" and costs up to $0.02 per request (maxAmountRequired of 20,000 base units of USDC with 6 decimals). Payment is handled via the x402 protocol: callers attach an `X-PAYMENT` header with a signed payment proof, and the server fulfills the request once payment is verified. No API keys, accounts, or rate limits are advertised.\n\nThe broader platform advertises four categories of endpoints: 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 are listed at $0.02 per request. Each endpoint accepts POST requests and returns `application/json`.\n\nThe specific functionality behind `/api/v1/inbox/12` is not documented beyond the generic \"Premium API Access\" label. There is no OpenAPI spec, no request/response schema, and the crawled docs pages (pricing, README, /api) all resolve to a wallet-connect prompt with no additional content. Prospective callers should be aware that the actual behavior of this particular endpoint is unclear from available documentation.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","json-api","no-api-key","post-method"],"categories":["api-marketplace","crypto-payments"],"synonyms":["x402 API","micropayment API","USDC pay-per-call","Base network API","lowpaymentfee","low payment fee API","402 payment required API"],"warnings":["No documentation exists for the specific endpoint /api/v1/inbox/12 — its actual functionality is unknown.","No OpenAPI or request/response schema is available for any endpoint on this platform.","Crawled /pricing, /README, and /api pages contain no useful content (only 'Connect wallet').","The 'Premium API Access' label is generic and does not describe what the endpoint returns."],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/12","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/inbox/12","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live (returns a valid 402 x402 challenge) and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI spec, no request/response schema, no documentation of what /api/v1/inbox/12 actually does, and crawled pages beyond the landing page are empty wallet-connect stubs. The listing is effectively a 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'/api/v1/inbox/12':58,180 '/call':18,36 '0.02':17,35,68,165 '000':74 '20':73 '402 payment required API' '6':80 'Base network API' 'USDC pay-per-call' 'accept':170 'access':63,189 'account':114 'actual':226 'addit':217 'advertis':119,123 'ai':11,29,135 'analysi':139 'analyt':129 'api':5,23,45,62,112,188 'application/json':175 'attach':90 'avail':235 'awar':223 'base':8,26,52,75 'base-network' 'behavior':227 'behind':179 'beyond':184 'broader':121 'caller':89,220 'categori':125 'classif':142 'collect':40 'connect':213 'content':218 'convers':159 'cost':65 'crawl':201 'data':10,28,128,132 'decim':81 'doc':202 'document':183,236 'embed':143 'enabl':44 'endpoint':15,33,46,56,127,169,231 'estim':153 'exchang':148 'export':133 'feed':147 'financ':12,30,144 'four':124 'fulfil':104 'function':178 'gas':152 'generat':160 'generic':186 'geocod':157 'handl':84 'header':95 'host':38 'infrastructur':155 'insight':134 'json-api' 'key':113 'label':60,190 'learn':137 'limit':117 'list':163 'low payment fee API' 'lowpaymentfee' 'lowpaymentfee.com':37 'machin':136 'maxamountrequir':71 'metric':130 'micropayment API' 'network':53 'no-api-key' 'openapi':194 'page':203 'particular':230 'pay':2,20 'pay-per-request':1,19 'payment':82,94,99,108 'per':3,21,69,166 'platform':122 'post':171 'post-method' 'premium':61,187 'price':146,204 'prompt':214 'proof':100 'prospect':219 'protocol':88 'quot':151 'rate':116,149 'readm':205 'report':131 'request':4,22,70,106,167,172 'request/response':197 'resolv':208 'return':174 'schema':198 'sentiment':138 'server':103 'settl':47 'sign':98 'spec':195 'specif':55,177 'suit':6,24 'summar':141 'text':140 'token':150 'unclear':233 'unit':76 'usdc':9,27,49,78 'usdc-settlement' 'util':14,32,156 'valid':158 'verifi':110 'via':85 'wallet':212 'wallet-connect':211 'web3':145 'x':93 'x-payment':92 'x402':43,87 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"4d73f1ca-8934-4e5d-9129-6d78444e7a00","listingId":"44ddfb10-df91-45bf-a71a-5a8549bdc639","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/inbox/12","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:20.417Z"}],"sources":[{"listingId":"44ddfb10-df91-45bf-a71a-5a8549bdc639","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/12","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:20.417Z","lastSeenAt":"2026-04-22T04:02:33.027Z"}],"details":{"listingId":"44ddfb10-df91-45bf-a71a-5a8549bdc639","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/12 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <signed-x402-payment-proof>\" \\\n  -d '{}'","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"Endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/inbox/12"},{"claim":"USDC asset contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/inbox/12"},{"claim":"All listed endpoints 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 in Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Programmatic access to pay-per-use API endpoints without account registration","Agent-driven API consumption with on-chain USDC micropayments","Integrating x402-compatible payment flows into automated workflows"],"bestFor":["Developers or agents that already hold USDC on Base and want frictionless API access","Use cases requiring no-signup, no-rate-limit API calls","Testing x402 payment protocol integrations"],"notFor":["Users who need detailed API documentation or guaranteed SLAs before calling","Callers who cannot transact in USDC on the Base network","High-volume batch workloads where $0.02/request adds up significantly"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:08.997Z"},"updatedAt":"2026-04-22T04:02:33.027Z"}}