{"id":"849c6ea0-37fb-4dd2-abeb-89e39ace04f0","shortId":"M4wQ8j","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 73) behind an x402 paywall. The endpoint accepts POST requests and returns JSON. Payment is settled in USDC on the Base network using the x402 \"exact\" scheme, with a maximum cost of $0.02 per request (20,000 base units of USDC with 6 decimals).\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 market data, and utility services — all priced at $0.02 per request with no API keys, no rate limits, and no minimum commitments. However, this specific endpoint (/api/v1/emails/73/attachments) is not listed on the provider's landing page among the advertised API categories, making its exact functionality and response format unclear.\n\nThe x402 challenge is live and well-formed: it returns a proper 402 with version 1 challenge, specifying USDC (contract 0x8335…2913) on Base, payable to address 0x1A2B…85F3 with a 300-second timeout. No OpenAPI schema, detailed documentation, or example responses were found in the crawl. The docs, API, pricing, and README pages all rendered only a \"Connect wallet\" prompt with no substantive content.","tags":[],"capabilities":["x402-payment","email-attachments","usdc-base","pay-per-request","json-response"],"categories":["data","email"],"synonyms":["email attachment API","x402 email endpoint","pay-per-call email","micropayment email access","Base USDC API","lowpaymentfee email"],"warnings":["This specific endpoint (/api/v1/emails/73/attachments) is not listed among the provider's advertised APIs — its purpose and data source are unknown.","No documentation, OpenAPI spec, or example responses are available; docs/pricing/README pages all show only 'Connect wallet'.","The endpoint targets a hardcoded email ID (73), suggesting it may be a demo or test resource rather than a general-purpose API.","Response schema is entirely unknown — no outputSchema fields beyond the HTTP method were provided."],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/73/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/73/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The x402 challenge is live and well-formed, confirming the endpoint exists and accepts payment. However, the specific endpoint (/api/v1/emails/73/attachments) is not documented anywhere on the site, there is no OpenAPI schema, no example request/response, and all documentation pages render only a wallet-connect prompt. The purpose and response format are 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'0.02':10,22,69,113 '000':73 '0x1a2b':182 '0x8335':175 '1':170 '20':72 '2913':176 '300':186 '402':167 '6':79 '73':37 '85f3':183 'Base USDC API' 'accept':44 'access':30 'address':181 'advertis':143 'ai/ml':97 'among':141 'analysi':100 'analyt':96 'api':93,118,144,204 'attach':3,15,33 'base':8,20,57,74,178 'behind':38 'broader':86 'call':92 'categori':145 'challeng':156,171 'classif':102 'commit':126 'connect':213 'content':219 'contract':174 'cost':67 'crawl':201 'data':95,106 'decim':80 'detail':192 'doc':203 'document':193 'email':2,14,32,35 'email attachment API' 'email-attachments' 'embed':103 'endpoint':26,43,130 'exact':62,148 'exampl':195 'finance/crypto':104 'form':162 'format':152 'found':198 'function':149 'host':84 'howev':127 'id':36 'infer':98 'json':49 'json-response' 'key':119 'land':139 'limit':122 'list':134 'live':158 'lowpaymentfee email' 'lowpaymentfee.com':28,83 'make':146 'market':105 'maximum':66 'micropay':6,18 'micropayment email access' 'minimum':125 'network':58 'openapi':190 'page':140,208 'pay':90 'pay-per-cal':89 'pay-per-call email' 'pay-per-request' 'payabl':179 'payment':50 'paywal':41 'per':11,23,70,91,114 'post':45 'price':111,205 'prompt':215 'proper':166 'provid':29,82,137 'rate':121 'readm':207 'render':210 'request':12,24,46,71,115 'respons':151,196 'retriev':1,13 'return':48,164 'schema':191 'scheme':63 'second':187 'sentiment':99 'servic':109 'settl':52 'span':94 'specif':34,129 'specifi':172 'substant':218 'suit':87 'summar':101 'timeout':188 'unclear':153 'unit':75 'usdc':54,77,173 'usdc-base' 'use':59 'util':108 'version':169 'via':4,16 'wallet':214 'well':161 'well-form':160 'x402':5,17,40,61,155 'x402 email endpoint' 'x402-payment'","prices":[{"id":"b14ae1df-07de-4957-8cf7-b679a4637ad4","listingId":"849c6ea0-37fb-4dd2-abeb-89e39ace04f0","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/73/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":"2026-04-21T18:32:12.576Z"}],"sources":[{"listingId":"849c6ea0-37fb-4dd2-abeb-89e39ace04f0","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/73/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:12.576Z","lastSeenAt":"2026-04-22T05:31:59.742Z"}],"details":{"listingId":"849c6ea0-37fb-4dd2-abeb-89e39ace04f0","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/73/attachments \\\n  -H \"X-PAYMENT: <x402-payment-token>\" \\\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 x402 challenge returns a 402 with maxAmountRequired of 20000 in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/emails/73/attachments"},{"claim":"USDC contract address on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/emails/73/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 provider offers APIs across data/analytics, AI/ML, finance/web3, and infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"Docs, API, pricing, and README pages render only a 'Connect wallet' prompt","source_url":"https://lowpaymentfee.com/docs"}],"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","Demonstrating x402 micropayment integration for data access"],"bestFor":["Agents or scripts that need one-off email attachment retrieval with instant crypto payment","Developers exploring x402 protocol integrations on Base","Use cases where no-signup, pay-per-request access is preferred"],"notFor":["Bulk email processing or mailbox management — this targets a single email ID","Users who need detailed documentation or guaranteed SLA before integrating","Non-crypto users who cannot pay in USDC on Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:20.512Z"},"updatedAt":"2026-04-22T05:31:59.742Z"}}