{"id":"f49d1d4c-92f0-404f-b3ad-5299f36da9ef","shortId":"S4KQZQ","kind":"x402","title":"Pay-per-request email attachment retrieval via x402 on Base (USDC).","tagline":"Pay-per-request email attachment retrieval via x402 on Base (USDC).","description":"This endpoint at lowpaymentfee.com provides access to email attachments via a POST request to `/api/v1/emails/42/attachments`. It is part of a broader platform offering dozens of pay-per-call API endpoints across data analytics, AI/ML, finance, infrastructure, and more — all settled on-chain using USDC on the Base network through the x402 protocol.\n\nThe specific endpoint listed here costs $0.02 per request (20,000 base units of USDC with 6 decimals). Payment is handled inline via the X-PAYMENT header; no API keys, subscriptions, or rate limits are required. The x402 challenge was successfully captured, confirming the endpoint is live and accepting payments to address `0x1A2B...85F3` using USDC (`0x8335...2913`) on Base.\n\nDocumentation is extremely sparse. The crawled docs, pricing, and API pages all returned only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema, and no explanation of what the email attachments endpoint actually returns or what input it expects. The endpoint path suggests retrieval of attachments for a specific email (ID 42), but whether this is a demo resource, a parameterized path, or something else is unclear. The platform's landing page confirms uniform $0.02 pricing and lists the endpoint categories but provides no per-endpoint documentation.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","email-attachments","pay-per-request","no-api-key"],"categories":["storage","email"],"synonyms":["email attachment API","x402 email endpoint","pay-per-call email","USDC API access","Base network API","lowpaymentfee email","402 payment email"],"warnings":["No OpenAPI or schema documentation available for this endpoint","All doc/pricing/API pages return only 'Connect wallet' with no technical content","The endpoint path '/api/v1/emails/42/attachments' is unexplained — unclear if '42' is a fixed demo ID or a parameterized path","No request body schema or response schema provided anywhere","Functionality of the email attachments endpoint is entirely unclear"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/42/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/42/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.250","qualityRationale":"The x402 challenge is live and pricing is clear ($0.02/request in USDC on Base), but there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page, and no explanation of what this specific endpoint does or accepts. This is effectively a stub 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'0.02':85,222 '000':89 '0x1a2b':132 '0x8335':136 '20':88 '2913':137 '402 payment email' '42':199 '6':95 '85f3':133 'Base network API' 'USDC API access' 'accept':128 'access':30 'across':56 'actual':180 'address':131 'ai/ml':59 'analyt':58 'api':54,108,149 'attach':6,18,33,178,193 'base':11,23,73,90,139 'base-network' 'broader':45 'call':53 'captur':121 'categori':228 'chain':68 'challeng':118 'confirm':122,220 'connect':155 'cost':84 'crawl':145 'data':57 'decim':96 'demo':205 'detail':162 'doc':146 'document':140,235 'dozen':48 'els':212 'email':5,17,32,177,197 'email attachment API' 'email-attachments' 'endpoint':26,55,81,124,179,188,227,234 'expect':186 'explan':173 'extrem':142 'financ':60 'handl':99 'header':106 'id':198 'infrastructur':61 'inlin':100 'input':184 'key':109 'land':218 'limit':113 'list':82,225 'live':126 'lowpaymentfee email' 'lowpaymentfee.com':28 'network':74 'no-api-key' 'offer':47 'on-chain':66 'openapi':166 'page':150,219 'parameter':208 'part':42 'path':189,209 'pay':2,14,51 'pay-per-cal':50 'pay-per-call email' 'pay-per-request':1,13 'payment':97,105,129 'per':3,15,52,86,233 'per-endpoint':232 'platform':46,216 'post':36 'price':147,223 'prompt':157 'protocol':78 'provid':29,230 'rate':112 'request':4,16,37,87 'request/response':169 'requir':115 'resourc':206 'retriev':7,19,191 'return':152,181 'schema':170 'settl':65 'someth':211 'spars':143 'spec':167 'specif':80,196 'subscript':110 'success':120 'suggest':190 'technic':161 'unclear':214 'uniform':221 'unit':91 'usdc':12,24,70,93,135 'usdc-settlement' 'use':69,134 'via':8,20,34,101 'wallet':156 'whether':201 'x':104 'x-payment':103 'x402':9,21,77,117 'x402 email endpoint' 'x402-payment'","prices":[{"id":"71a90c0c-5da5-470f-a856-cc55b4862339","listingId":"f49d1d4c-92f0-404f-b3ad-5299f36da9ef","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/42/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":"2026-04-21T18:32:12.436Z"}],"sources":[{"listingId":"f49d1d4c-92f0-404f-b3ad-5299f36da9ef","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/42/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:12.436Z","lastSeenAt":"2026-04-22T01:02:05.113Z"}],"details":{"listingId":"f49d1d4c-92f0-404f-b3ad-5299f36da9ef","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/42/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 endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/42/attachments"},{"claim":"Uniform pricing of $0.02 per request across all endpoints, no API keys, no rate limits","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/emails/42/attachments"}],"useCases":["Retrieving email attachments programmatically with per-request crypto payment","Agent-driven workflows that need to fetch email data without subscription overhead","Integrating on-chain micropayments for document/attachment access"],"bestFor":["Developers wanting zero-signup, pay-as-you-go email attachment access","AI agents that can settle x402 payments autonomously on Base","Prototyping workflows that need instant API access without API key management"],"notFor":["Production systems requiring detailed API documentation and SLAs","Users who need bulk email processing at high volume with predictable costs","Anyone without a Base-compatible USDC wallet"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:20.755Z"},"updatedAt":"2026-04-22T01:02:05.113Z"}}