{"id":"23e4d714-6ab2-42d8-822d-3d93c0c66dd3","shortId":"cbRJtC","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 27) 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 (maxAmountRequired of 20,000 base units with 6 decimals = $0.02), with no API keys, rate limits, or subscriptions required.\n\nThe provider lowpaymentfee.com hosts a broader suite of pay-per-call APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/crypto data feeds, and infrastructure utilities — all priced at $0.02 per request via the x402 protocol. However, this specific endpoint is narrowly scoped to retrieving attachments for a single email resource (email 27). Documentation beyond the landing page is essentially empty (all subpages just show a \"Connect wallet\" prompt), so the exact request body schema, response format, and what data the attachments contain are unknown.\n\nThe endpoint is confirmed live: it returns a well-formed x402 version 1 challenge with USDC (contract 0x8335…) on Base. The payment recipient is 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout.","tags":[],"capabilities":["x402-payment","email-attachments","usdc-base","pay-per-request","no-api-key"],"categories":["data","email"],"synonyms":["email attachment API","x402 email","pay-per-call email","micropayment email API","Base USDC API","lowpaymentfee"],"warnings":["No documentation available — all subpages render only 'Connect wallet'","Endpoint is scoped to a single hardcoded email ID (27); unclear if this is a demo or production resource","No request body schema or response schema documented","Unknown what 'attachments' data is actually returned","Provider site lists many API categories but none appear documented beyond the landing page"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/27/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/27/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 challenge, but documentation is effectively nonexistent — all doc/pricing/API pages show only 'Connect wallet'. The endpoint path is very specific (single email ID 27) with no explanation of what data it serves, no request/response schema, and no examples. This is essentially a stub 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'000':66 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':195 '0x8335':188 '1':183 '20':65 '27':37,137 '300':198 '6':70 'Base USDC API' 'accept':44 'access':30 'ai/ml':98 'analysi':101 'analyt':97 'api':75,94 'attach':3,15,33,130,166 'base':8,20,57,67,190 'behind':38 'beyond':139 'bodi':158 'broader':87 'call':62,93 'challeng':184 'classif':103 'confirm':173 'connect':151 'contain':167 'contract':187 'data':96,106,164 'decim':71 'document':138 'email':2,14,32,35,134,136 'email attachment API' 'email-attachments' 'embed':104 'empti':145 'endpoint':26,43,124,171 'essenti':144 'exact':156 'feed':107 'finance/crypto':105 'form':180 'format':161 'host':85 'howev':121 'id':36 'infer':99 'infrastructur':109 'json':49 'key':76 'land':141 'limit':78 'live':174 'lowpaymentfee' 'lowpaymentfee.com':28,84 'maxamountrequir':63 'micropay':6,18 'micropayment email API' 'narrowli':126 'network':58 'no-api-key' 'page':142 'pay':91 'pay-per-cal':90 'pay-per-call email' 'pay-per-request' 'payment':50,192 'paywal':41 'per':11,23,61,92,115 'post':45 'price':112 'prompt':153 'protocol':120 'provid':29,83 'rate':77 'recipi':193 'request':12,24,46,116,157 'requir':81 'resourc':135 'respons':160 'retriev':1,13,129 'return':48,176 'schema':159 'scope':127 'second':199 'sentiment':100 'settl':52 'show':149 'singl':133 'span':95 'specif':34,123 'subpag':147 'subscript':80 'suit':88 'summar':102 'timeout':200 'unit':68 'unknown':169 'usdc':54,186 'usdc-base' 'util':110 'version':182 'via':4,16,117 'wallet':152 'well':179 'well-form':178 'x402':5,17,40,119,181 'x402 email' 'x402-payment'","prices":[{"id":"b8535c1d-7eb4-49e9-97f3-76c4c5309a2f","listingId":"23e4d714-6ab2-42d8-822d-3d93c0c66dd3","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/27/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":"2026-04-21T18:32:11.093Z"}],"sources":[{"listingId":"23e4d714-6ab2-42d8-822d-3d93c0c66dd3","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/27/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:11.093Z","lastSeenAt":"2026-04-22T10:02:44.850Z"}],"details":{"listingId":"23e4d714-6ab2-42d8-822d-3d93c0c66dd3","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/27/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":"Endpoint returns x402 v1 challenge with maxAmountRequired 20000 in USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/27/attachments"},{"claim":"All APIs priced at $0.02 per request with no API keys, no rate limits, instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/emails/27/attachments"}],"useCases":["Programmatically retrieving email attachments without authentication or subscriptions","Agent-driven workflows that need to fetch specific email attachment data on demand","Demonstrating x402 micropayment integration for data retrieval"],"bestFor":["Developers experimenting with x402 payment protocol","Agents needing one-shot access to email attachment data","Low-friction pay-per-use data access without API key management"],"notFor":["Bulk email processing or mailbox-level access","Users needing detailed API documentation or guaranteed SLA","Accessing arbitrary emails — this endpoint is scoped to email ID 27 only"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:21.367Z"},"updatedAt":"2026-04-22T10:02:44.850Z"}}