{"id":"c4a8cf6b-3d46-4d4c-872b-dc7b51c0fa6b","shortId":"Rk5Hsq","kind":"x402","title":"Retrieve email attachments via x402 micropayment on Base for $0.02 per request.","tagline":"Retrieve email attachments via x402 micropayment on Base for $0.02 per request.","description":"This endpoint at lowpaymentfee.com provides access to email attachment data (specifically email ID 57) behind an x402 paywall. The endpoint accepts POST requests and returns JSON. Payment is settled in USDC on the Base network at $0.02 per call (20,000 base units with 6 decimals). No API keys or rate limits are required — callers simply include an X-PAYMENT header with a valid x402 payment proof.\n\nThe broader lowpaymentfee.com platform advertises a suite of pay-per-call APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/crypto market data, and utility services (geocoding, validation, conversion, generation), all priced at $0.02 per request. However, this specific endpoint — `/api/v1/emails/57/attachments` — is not listed on the site's public catalog, and no documentation describes its request body schema, expected parameters, or response format. The endpoint is live and returns a proper x402 challenge, but the actual functionality behind the paywall is undocumented.\n\nBecause there is no OpenAPI spec, no request/response examples, and no documentation beyond the generic \"Premium API Access\" label, the precise behavior of this endpoint is unclear. Callers should treat this as an opaque paid endpoint until more documentation surfaces.","tags":[],"capabilities":["x402-payment","usdc-base","email-attachments","pay-per-request","no-api-key"],"categories":["data","email"],"synonyms":["email attachment API","x402 email endpoint","paid email data","lowpaymentfee email","micropayment email API","Base USDC API"],"warnings":["This specific endpoint (/api/v1/emails/57/attachments) is not listed in the provider's public API catalog — its purpose and data source are unclear.","No request body schema or response schema is documented anywhere.","The docs, pricing, API, and README pages all render only a 'Connect wallet' prompt with no useful content.","The hardcoded email ID '57' suggests this may be a demo or test endpoint rather than a general-purpose API."],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/57/attachments","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/57/attachments","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 OpenAPI spec, no request/response schema, no documentation for this specific route, and the endpoint path (emails/57/attachments) is not listed in the site's public catalog. Functionality is essentially unknown beyond the payment 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'0.02':10,22,61,129 '000':65 '20':64 '57':38 '6':69 'Base USDC API' 'accept':45 'access':30,195 'actual':171 'advertis':97 'ai/ml':109 'analysi':112 'analyt':108 'api':72,105,194 'attach':3,15,33 'base':8,20,58,66 'behavior':199 'behind':39,173 'beyond':190 'bodi':152 'broader':94 'call':63,104 'caller':79,205 'catalog':145 'challeng':168 'classif':114 'convers':124 'data':34,107,118 'decim':70 'describ':149 'document':148,189,216 'email':2,14,32,36 'email attachment API' 'email-attachments' 'embed':115 'endpoint':26,44,135,160,202,213 'exampl':186 'expect':154 'finance/crypto':116 'format':158 'function':172 'generat':125 'generic':192 'geocod':122 'header':86 'howev':132 'id':37 'includ':81 'infer':110 'json':50 'key':73 'label':196 'limit':76 'list':139 'live':162 'lowpaymentfee email' 'lowpaymentfee.com':28,95 'market':117 'micropay':6,18 'micropayment email API' 'network':59 'no-api-key' 'opaqu':211 'openapi':182 'paid':212 'paid email data' 'paramet':155 'pay':102 'pay-per-cal':101 'pay-per-request' 'payment':51,85,91 'paywal':42,175 'per':11,23,62,103,130 'platform':96 'post':46 'precis':198 'premium':193 'price':127 'proof':92 'proper':166 'provid':29 'public':144 'rate':75 'request':12,24,47,131,151 'request/response':185 'requir':78 'respons':157 'retriev':1,13 'return':49,164 'schema':153 'sentiment':111 'servic':121 'settl':53 'simpli':80 'site':142 'span':106 'spec':183 'specif':35,134 'suit':99 'summar':113 'surfac':217 'treat':207 'unclear':204 'undocu':177 'unit':67 'usdc':55 'usdc-base' 'util':120 'valid':89,123 'via':4,16 'x':84 'x-payment':83 'x402':5,17,41,90,167 'x402 email endpoint' 'x402-payment'","prices":[{"id":"635b0a43-893a-4f64-9015-c4364af7e861","listingId":"c4a8cf6b-3d46-4d4c-872b-dc7b51c0fa6b","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/57/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:12.327Z"}],"sources":[{"listingId":"c4a8cf6b-3d46-4d4c-872b-dc7b51c0fa6b","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/57/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:12.327Z","lastSeenAt":"2026-04-22T07:01:53.673Z"}],"details":{"listingId":"c4a8cf6b-3d46-4d4c-872b-dc7b51c0fa6b","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/57/attachments \\\n  -H \"X-PAYMENT: <x402-payment-proof>\" \\\n  -H \"Content-Type: application/json\"","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 in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/emails/57/attachments"},{"claim":"The platform advertises $0.02 per request pricing with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/57/attachments"}],"useCases":["Retrieving attachments from a specific email record via programmatic API call","Agent-driven workflows that need to fetch email attachment data without API key provisioning","Pay-per-use access to email content behind a crypto micropayment wall"],"bestFor":["Agents or scripts that need one-off email attachment retrieval without signup","Developers experimenting with x402 payment protocol on Base","Workflows requiring keyless, pay-as-you-go API access"],"notFor":["Bulk email processing or mailbox-level access — this targets a single email ID","Users who need detailed API documentation or guaranteed SLAs before integrating"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:20.882Z"},"updatedAt":"2026-04-22T07:01:53.673Z"}}