{"id":"bc1adac2-ae44-4a13-8760-b2ef5bfe6e67","shortId":"XhFe2U","kind":"x402","title":"Pay-per-call notification endpoint on Base via x402 — $0.02 per request in USDC.","tagline":"Pay-per-call notification endpoint on Base via x402 — $0.02 per request in USDC.","description":"This endpoint at `/api/v1/notifications/21` is part of the lowpaymentfee.com platform, which offers a collection of pay-per-request APIs settled via the x402 protocol on the Base network using USDC. The specific endpoint is described as \"Premium API Access\" and accepts POST requests. Payment is $0.02 per call (20,000 base units of USDC with 6 decimals), settled on-chain to a specified wallet address. No API keys or rate limits are required — callers simply attach an X-PAYMENT header with the appropriate x402 payment proof.\n\nThe broader lowpaymentfee.com platform advertises endpoints across several 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 (geocoding, validation, conversion, generation). All endpoints are listed at $0.02 per request. However, this specific listing covers only the `/api/v1/notifications/21` endpoint, whose exact functionality beyond \"Premium API Access\" is not documented.\n\nThe endpoint is live and returned a proper 402 challenge when probed. The x402 challenge specifies scheme \"exact\", network \"base\", asset USDC (contract 0x8335…), and a max timeout of 300 seconds. No OpenAPI schema, detailed documentation, or example responses were found in the crawl.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","no-api-key","notifications"],"categories":["notifications","infrastructure"],"synonyms":["lowpaymentfee","x402 notification api","pay-per-call api","micropayment api","base usdc api","premium api access","notification endpoint"],"warnings":["No documentation found for /api/v1/notifications/21 — its actual functionality is unknown","No request body schema or response schema available","No OpenAPI spec, README, or detailed docs were accessible from the crawl","The endpoint name 'Premium API Access' is generic and does not describe what it does","The platform lists many endpoint categories but none match a 'notifications' path, raising questions about this endpoint's purpose"],"endpointUrl":"https://lowpaymentfee.com/api/v1/notifications/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/notifications/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 it is operational. However, there is no documentation on what the notifications/21 endpoint actually does, no request/response schema, and no examples. The crawl pages beyond the homepage returned only 'Connect wallet' with no useful content. The endpoint's purpose is essentially unknown beyond its generic 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'0.02':11,26,77,166 '000':81 '0x8335':211 '20':80 '300':217 '402':196 '6':87 'accept':72 'access':70,184 'across':126 'address':97 'advertis':124 'ai':136 'analysi':140 'analyt':130 'api':50,69,99,183 'appropri':116 'asset':208 'attach':108 'base':8,23,58,82,207 'base usdc api' 'base-network' 'beyond':181 'broader':121 'call':4,19,79 'caller':106 'categori':128 'chain':92 'challeng':197,202 'classif':143 'collect':44 'contract':210 'convers':159 'cover':173 'crawl':231 'data':129,133 'decim':88 'describ':66 'detail':222 'document':187,223 'embed':144 'endpoint':6,21,32,64,125,162,177,189 'estim':154 'exact':179,205 'exampl':225 'exchang':149 'export':134 'feed':148 'financ':145 'found':228 'function':180 'gas':153 'generat':160 'geocod':157 'header':113 'howev':169 'infrastructur':156 'insight':135 'key':100 'learn':138 'limit':103 'list':164,172 'live':191 'lowpaymentfee' 'lowpaymentfee.com':39,122 'machin':137 'max':214 'metric':131 'micropayment api' 'network':59,206 'no-api-key' 'notif':5,20 'notification endpoint' 'notifications' 'offer':42 'on-chain':90 'openapi':220 'part':36 'pay':2,17,47 'pay-per-cal':1,16 'pay-per-call api' 'pay-per-request':46 'payment':75,112,118 'per':3,12,18,27,48,78,167 'platform':40,123 'post':73 'premium':68,182 'premium api access' 'price':147 'probe':199 'proof':119 'proper':195 'protocol':55 'quot':152 'rate':102,150 'report':132 'request':13,28,49,74,168 'requir':105 'respons':226 'return':193 'schema':221 'scheme':204 'second':218 'sentiment':139 'settl':51,89 'sever':127 'simpli':107 'specif':63,171 'specifi':95,203 'summar':142 'text':141 'timeout':215 'token':151 'unit':83 'usdc':15,30,61,85,209 'usdc-settlement' 'use':60 'valid':158 'via':9,24,52 'wallet':96 'web3':146 'whose':178 'x':111 'x-payment':110 'x402':10,25,54,117,201 'x402 notification api' 'x402-payment'","prices":[{"id":"f7e4c81b-029d-4e7f-a3b0-3b7072d1fd81","listingId":"bc1adac2-ae44-4a13-8760-b2ef5bfe6e67","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/notifications/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":"2026-04-21T18:32:32.292Z"}],"sources":[{"listingId":"bc1adac2-ae44-4a13-8760-b2ef5bfe6e67","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/notifications/21","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:32.292Z","lastSeenAt":"2026-04-22T04:02:46.761Z"}],"details":{"listingId":"bc1adac2-ae44-4a13-8760-b2ef5bfe6e67","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/notifications/21 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\" \\\n  -d '{}'","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/notifications/21"},{"claim":"All endpoints on the platform are priced at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/notifications/21"}],"useCases":["Sending or triggering notifications via a pay-per-call model without needing an API key","Integrating notification delivery into agent workflows that settle payments on Base","Testing x402 protocol integrations with a low-cost endpoint"],"bestFor":["Developers experimenting with x402 payment protocol","Agents needing keyless, pay-per-use notification endpoints","Low-volume notification use cases where $0.02/call is acceptable"],"notFor":["High-volume notification systems where per-call costs would accumulate significantly","Users who need detailed documentation or guaranteed SLAs before integrating"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:12:51.194Z"},"updatedAt":"2026-04-22T04:02:46.761Z"}}