{"id":"a830c0ea-291a-42e5-bf94-9e4c734bcce6","shortId":"tbM2Ey","kind":"x402","title":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","tagline":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","description":"This endpoint at lowpaymentfee.com provides \"Premium API Access\" via the x402 payment protocol. The specific path `/api/v1/inbox/167` is one of many endpoints offered by the platform, which advertises a broad catalog spanning data & analytics, AI & machine learning (sentiment analysis, 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, paid in USDC on the Base network with no API keys, no rate limits, and no commitments required.\n\nThe x402 challenge is live and returns a 402 with `maxAmountRequired` of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, which has 6 decimals), equating to $0.02 per call. Payment is made via the `exact` scheme to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout. The endpoint accepts HTTP POST and returns `application/json`.\n\nNote that while the landing page lists many distinct API paths across multiple categories, the specific functionality behind `/api/v1/inbox/167` is not documented beyond the generic label \"Premium API Access.\" There is no OpenAPI spec, no request/response schema, and no usage examples available from the crawled pages. The broader platform appears to be a demonstration or marketplace of x402-gated microservices, but without detailed documentation it is difficult to confirm what data or computation this particular endpoint returns.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","json-response","http-post"],"categories":["api-marketplace","infrastructure"],"synonyms":["lowpaymentfee","x402 api","micropayment api","pay-per-call api","USDC api access","base network api"],"warnings":["No OpenAPI or schema documentation available for this endpoint","The specific functionality of /api/v1/inbox/167 is undocumented — 'Premium API Access' is a generic label","No request or response examples are available","Crawled /api, /pricing, and /README pages returned no meaningful content beyond 'Connect wallet'","The platform lists many endpoint categories but it is unclear whether they are all functional"],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/167","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/167","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 pricing is clear ($0.02 USDC on Base), but there is no OpenAPI spec, no request/response schema, no documentation of what /api/v1/inbox/167 actually does, and crawled subpages returned only 'Connect wallet' with no useful content. The endpoint is effectively a stub 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'/request':13,28 '0.02':12,27,95,141 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':153 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':134 '20000':128 '300':156 '402':124 '6':137 'USDC api access' 'accept':161 'access':7,22,38,195 'across':178 'address':152 'advertis':58 'ai':65 'analysi':69 'analyt':64 'api':6,21,37,107,176,194 'appear':216 'application/json':166 'asset':133 'avail':208 'base':9,24,103,129 'base network api' 'behind':184 'beyond':189 'broad':60 'broader':214 'call':4,19,143 'catalog':61 'categori':180 'challeng':118 'classif':71 'commit':114 'comput':240 'confirm':236 'convers':88 'crawl':211 'data':63,238 'decim':138 'demonstr':220 'detail':230 'difficult':234 'distinct':175 'document':188,231 'embed':72 'endpoint':32,52,91,160,243 'equat':139 'estim':82 'exact':149 'exampl':207 'exchang':77 'feed':76 'financ':73 'function':183 'gas':81 'gate':226 'generat':89 'generic':191 'geocod':86 'http':162 'http-post' 'infrastructur':84 'json-response' 'key':108 'label':192 'land':171 'learn':67 'limit':111 'list':173 'live':120 'lowpaymentfee' 'lowpaymentfee.com':34 'machin':66 'made':146 'mani':51,174 'marketplac':222 'maxamountrequir':126 'micropayment api' 'microservic':227 'multipl':179 'network':104 'note':167 'offer':53 'one':49 'openapi':199 'page':172,212 'paid':98 'particular':242 'path':46,177 'pay':2,17 'pay-per-cal':1,16 'pay-per-call api' 'pay-per-request' 'payment':42,144 'per':3,18,96,142 'platform':56,215 'post':163 'premium':5,20,36,193 'price':75,93 'protocol':43 'provid':35 'quot':80 'rate':78,110 'request':97 'request/response':202 'requir':115 'return':122,165,244 'schema':203 'scheme':150 'second':157 'sentiment':68 'span':62 'spec':200 'specif':45,182 'summar':70 'timeout':158 'token':79 'unit':130 'usag':206 'usdc':15,30,100,132 'usdc-base' 'util':85 'valid':87 'via':10,25,39,147 'web3':74 'without':229 'x402':11,26,41,117,225 'x402 api' 'x402-gated':224 'x402-payment'","prices":[{"id":"b4e8deaf-9eb0-4fe5-a700-9908285c4622","listingId":"a830c0ea-291a-42e5-bf94-9e4c734bcce6","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/167","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:20.741Z"}],"sources":[{"listingId":"a830c0ea-291a-42e5-bf94-9e4c734bcce6","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/167","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:20.741Z","lastSeenAt":"2026-04-22T07:02:02.645Z"}],"details":{"listingId":"a830c0ea-291a-42e5-bf94-9e4c734bcce6","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/167 \\\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 priced at $0.02 per request with no API keys, no rate limits, instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"Platform offers APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"x402 challenge returns maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base network","source_url":"https://lowpaymentfee.com/api/v1/inbox/167"}],"useCases":["Programmatic access to premium API services without API key management","Agent-driven pay-per-call workflows settled in USDC on Base","Testing x402 payment protocol integrations with low-cost endpoints"],"bestFor":["Developers exploring x402 payment protocol","AI agents needing keyless, pay-per-use API access","Low-cost micropayment API experimentation on Base"],"notFor":["Users needing well-documented, schema-specified API contracts","High-throughput production workloads requiring SLA guarantees","Users without USDC on Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:08.493Z"},"updatedAt":"2026-04-22T07:02:02.645Z"}}