{"id":"d15684cc-82dc-493a-94df-97e8247ca19f","shortId":"ULMcCw","kind":"x402","title":"x402-gated email endpoint on Base, pay $0.02 per request in USDC — no API keys required.","tagline":"x402-gated email endpoint on Base, pay $0.02 per request in USDC — no API keys required.","description":"This endpoint at `/api/v1/emails/4` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-request APIs settled in USDC on the Base network. The specific purpose of the `/emails/4` route is not documented beyond the generic label \"Premium API Access,\" so its exact functionality is unclear. It likely provides some form of email-related data or service, but no schema, example payloads, or detailed documentation are available.\n\nThe endpoint is live and returns a valid x402 challenge (HTTP 402) requesting payment of up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 per request given USDC's 6 decimals. Payment is made via the x402 `exact` scheme with a 300-second timeout. No API keys, rate limits, or subscriptions are required — callers simply attach an `X-PAYMENT` header with a valid payment proof.\n\nThe broader lowpaymentfee.com platform advertises endpoints across data/analytics, AI/ML (sentiment, summarization, classification, embeddings), finance/Web3 (price feeds, exchange rates, gas estimates), and infrastructure utilities (geocoding, validation, conversion). All are priced at $0.02 per call. However, documentation pages (`/docs`, `/pricing`, `/README`) returned only a \"Connect wallet\" prompt with no substantive content, so the actual capabilities and response formats of these endpoints remain unverified.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","email-api","no-api-key"],"categories":["email","data"],"synonyms":["email API","premium email access","x402 email","pay-per-call email","lowpaymentfee email","USDC email endpoint"],"warnings":["The exact functionality of /api/v1/emails/4 is undocumented — 'Premium API Access' is a generic label applied to all endpoints on this platform.","All documentation pages (/docs, /pricing, /README) returned no substantive content, only a 'Connect wallet' prompt.","No request body schema or response schema is available; callers must guess at the expected input format.","The broader platform lists many endpoint categories (AI, finance, infrastructure) but none appear to have public documentation verifying their functionality."],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/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/emails/4","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.250","qualityRationale":"The endpoint is live and returns a valid x402 challenge, but there is no documentation, no request/response schema, and no explanation of what the /emails/4 endpoint actually does. The docs, pricing, and README pages are all empty beyond a wallet-connect prompt. This is effectively a stub 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'/docs':216 '/emails/4':68 '/pricing':217 '/readme':218 '0.02':9,26,137,210 '000':126 '0x8335':131 '20':125 '2913':132 '300':155 '402':119 '6':143 'USDC email endpoint' 'access':79 'across':186 'actual':231 'advertis':184 'ai/ml':188 'api':15,32,55,78,159 'attach':169 'avail':107 'base':7,24,61,127,134 'base-network' 'beyond':73 'broader':181 'call':212 'caller':167 'capabl':232 'challeng':117 'classif':191 'collect':46 'connect':222 'content':228 'convers':205 'data':95 'data/analytics':187 'decim':144 'detail':104 'document':72,105,214 'email':4,21,93 'email API' 'email-api' 'email-rel':92 'embed':192 'endpoint':5,22,36,109,185,238 'equal':136 'estim':199 'exact':82,151 'exampl':101 'exchang':196 'feed':195 'finance/web3':193 'form':90 'format':235 'function':83 'gas':198 'gate':3,20 'generic':75 'geocod':203 'given':140 'header':174 'howev':213 'http':118 'infrastructur':201 'key':16,33,160 'label':76 'like':87 'limit':162 'live':111 'lowpaymentfee email' 'lowpaymentfee.com':43,182 'made':147 'network':62 'no-api-key' 'page':215 'part':40 'pay':8,25,52 'pay-per-call email' 'pay-per-request':51 'payload':102 'payment':121,145,173,178 'per':10,27,53,138,211 'platform':44,183 'premium':77 'premium email access' 'price':194,208 'prompt':224 'proof':179 'protocol':50 'provid':88 'purpos':65 'rate':161,197 'relat':94 'remain':239 'request':11,28,54,120,139 'requir':17,34,166 'respons':234 'return':113,219 'rout':69 'schema':100 'scheme':152 'second':156 'sentiment':189 'servic':97 'settl':56 'simpli':168 'specif':64 'subscript':164 'substant':227 'summar':190 'timeout':157 'unclear':85 'unit':128 'unverifi':240 'usdc':13,30,58,130,141 'usdc-settlement' 'util':202 'valid':115,177,204 'via':148 'wallet':223 'x':172 'x-payment':171 'x402':2,19,49,116,150 'x402 email' 'x402-gated':1,18 'x402-payment' 'x402-protocol':48","prices":[{"id":"039fe97a-c5e2-4719-9a40-7881bbdf83e7","listingId":"d15684cc-82dc-493a-94df-97e8247ca19f","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/emails/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":"2026-04-21T18:32:11.277Z"}],"sources":[{"listingId":"d15684cc-82dc-493a-94df-97e8247ca19f","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/4","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:11.277Z","lastSeenAt":"2026-04-22T09:02:00.990Z"}],"details":{"listingId":"d15684cc-82dc-493a-94df-97e8247ca19f","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/4 \\\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 valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/4"},{"claim":"All APIs on the platform are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/4"},{"claim":"Documentation pages (/docs, /pricing, /README) returned only 'Connect wallet' with no substantive content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Fetching email-related data or performing email operations on a per-request payment basis","Agent-driven workflows that need email functionality without managing API keys or subscriptions","Programmatic access to email services settled in USDC on Base L2"],"bestFor":["Developers or agents wanting zero-signup, pay-per-use email API access","x402-compatible agents that can settle USDC payments on Base","Low-volume or sporadic email data needs where $0.02/request is cost-effective"],"notFor":["High-volume email sending or marketing automation (no bulk pricing or documented throughput)","Users who need detailed API documentation, schemas, or guaranteed SLAs before integrating","Non-crypto users who cannot settle payments in USDC on Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:21.124Z"},"updatedAt":"2026-04-22T09:02:00.990Z"}}