{"id":"def9179a-3b07-48d5-a89b-d0691839f93e","shortId":"dH5QhL","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 attachments (specifically email ID 67) behind an x402 paywall. The payment is settled in USDC on the Base network using the \"exact\" scheme. The x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (6 decimals), which equals $0.02 per request. The endpoint accepts POST requests and returns application/json.\n\nThe broader lowpaymentfee.com platform hosts a variety of pay-per-call API endpoints spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/crypto data feeds, and utility services — all priced at $0.02 per request with no API keys, no rate limits, and no commitments required. However, this specific listing is for the email attachments endpoint (`/api/v1/emails/67/attachments`), which is not prominently documented on the site's landing page. Its exact input parameters and response schema are not documented in the crawled material, so the precise request body format and attachment data structure are unknown.\n\nPayment is made via the x402 protocol's X-PAYMENT header, settling to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using USDC (contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base. The endpoint is live and returned a proper 402 challenge during probing.","tags":[],"capabilities":["x402-payment","usdc-base","email-attachments","pay-per-request","no-api-key"],"categories":["data","email"],"synonyms":["email attachment API","x402 email endpoint","pay-per-call email","micropayment email API","USDC email attachments","Base network API","lowpaymentfee"],"warnings":["This endpoint references a specific email ID (67) in the path; it is unclear whether this is a demo or a production resource.","No request body schema or response schema is documented anywhere in the crawled material.","The site's docs, API, pricing, and README pages all returned only 'Connect wallet' with no substantive content.","This specific endpoint (/api/v1/emails/67/attachments) is not listed among the site's advertised APIs on the landing page."],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/67/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/67/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live and returns a valid x402 402 challenge, but there is no documentation for this specific email attachments endpoint — no input schema, no response schema, no examples. The endpoint path references a hardcoded email ID (67), and the crawled site pages are mostly empty ('Connect wallet'). The purpose and data returned are 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'0.02':10,22,73,117 '000':64 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':194 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':198 '20':63 '402':209 '6':69 '67':37 'Base network API' 'USDC email attachments' 'accept':78 'access':30 'address':193 'advertis':59 'ai/ml':101 'analysi':104 'analyt':100 'api':96,122 'application/json':83 'attach':3,15,33,139,174 'base':8,20,50,65,200 'behind':38 'bodi':171 'broader':85 'call':95 'challeng':58,210 'classif':106 'commit':129 'contract':197 'crawl':165 'data':99,109,175 'decim':70 'document':146,162 'email':2,14,32,35,138 'email attachment API' 'email-attachments' 'embed':107 'endpoint':26,77,97,140,202 'equal':72 'exact':54,154 'feed':110 'finance/crypto':108 'format':172 'header':190 'host':88 'howev':131 'id':36 'infer':102 'input':155 'key':123 'land':151 'limit':126 'list':134 'live':204 'lowpaymentfee' 'lowpaymentfee.com':28,86 'made':181 'materi':166 'maxamountrequir':61 'micropay':6,18 'micropayment email API' 'network':51 'no-api-key' 'page':152 'paramet':156 'pay':93 'pay-per-cal':92 'pay-per-call email' 'pay-per-request' 'payment':43,179,189 'paywal':41 'per':11,23,74,94,118 'platform':87 'post':79 'precis':169 'price':115 'probe':212 'promin':145 'proper':208 'protocol':185 'provid':29 'rate':125 'request':12,24,75,80,119,170 'requir':130 'respons':158 'retriev':1,13 'return':82,206 'schema':159 'scheme':55 'sentiment':103 'servic':113 'settl':45,191 'site':149 'span':98 'specif':34,133 'structur':176 'summar':105 'unit':66 'unknown':178 'usdc':47,68,196 'usdc-base' 'use':52,195 'util':112 'varieti':90 'via':4,16,182 'x':188 'x-payment':187 'x402':5,17,40,57,184 'x402 email endpoint' 'x402-payment'","prices":[{"id":"93d33bc4-be25-4d16-a919-8342e2379efe","listingId":"def9179a-3b07-48d5-a89b-d0691839f93e","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/67/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":"2026-04-21T18:32:12.753Z"}],"sources":[{"listingId":"def9179a-3b07-48d5-a89b-d0691839f93e","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/67/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:12.753Z","lastSeenAt":"2026-04-22T04:02:25.509Z"}],"details":{"listingId":"def9179a-3b07-48d5-a89b-d0691839f93e","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/67/attachments \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-token>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The x402 challenge advertises maxAmountRequired of 20000 base units of USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/emails/67/attachments"},{"claim":"USDC contract address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/emails/67/attachments"},{"claim":"All listed APIs on the site are priced at $0.02 per request with no API keys, no rate limits","source_url":"https://lowpaymentfee.com"},{"claim":"The site advertises endpoints across data/analytics, AI/ML, finance/web3, and infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Retrieving email attachments programmatically via micropayment","Agent-driven email data extraction without API key management","Paying per-request for email content access on Base L2"],"bestFor":["Agents needing on-demand email attachment retrieval with crypto micropayments","Developers wanting keyless, pay-as-you-go email data access","x402-compatible wallets and clients on Base network"],"notFor":["Bulk email processing requiring thousands of requests at lower cost","Users who need detailed API documentation and schema guarantees before integrating","Non-crypto payment workflows (no fiat option available)"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:20.265Z"},"updatedAt":"2026-04-22T04:02:25.509Z"}}