{"id":"cac78abd-e67d-4f6d-b7a4-88e170586616","shortId":"jwH5vw","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 28) behind an x402 paywall. The endpoint accepts POST requests and returns JSON. Payment is settled on the Base network using USDC (USD Coin) at a cost of $0.02 per request (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 wide range of x402-gated API endpoints across categories including data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance and crypto market data, and infrastructure utilities. All endpoints on the platform share the same $0.02/request pricing model with no minimums or commitments. However, this specific listing covers only the `/api/v1/emails/28/attachments` endpoint.\n\nDocumentation on the site is extremely sparse — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI schema, no request/response examples, and no description of what the email attachments endpoint actually returns or what input parameters it expects. The endpoint is live (returning a valid 402 challenge), but the lack of documentation makes it difficult to use without experimentation.","tags":[],"capabilities":["x402-payment","email-attachments","base-network","usdc-settlement","micropayment","post-endpoint"],"categories":["data","email"],"synonyms":["email attachment API","x402 email endpoint","paid email API","lowpaymentfee email","micropayment email attachments","Base USDC API"],"warnings":["No API documentation available — docs, API, pricing, and README pages all show only 'Connect wallet'","No OpenAPI or schema describing request parameters or response format","The endpoint path references a hardcoded email ID (28), purpose unclear","No request or response examples available anywhere in crawled content","Cannot verify what data this endpoint actually returns"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/28/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/28/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 402 challenge, but there is zero documentation on request parameters, response format, or what 'emails/28/attachments' actually provides. No OpenAPI spec, no examples, and all doc pages are empty. This is effectively a stub 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'/request':140 '0.02':10,22,65,139 '000':69 '20':68 '28':37 '402':215 '6':73 'Base USDC API' 'accept':44 'access':30 'across':111 'actual':200 'advertis':101 'ai/ml':116 'analysi':119 'analyt':115 'api':76,109,166 'attach':3,15,33,198 'base':8,20,55,70 'base-network' 'behind':38 'broader':98 'caller':83 'categori':112 'challeng':216 'classif':121 'coin':60 'commit':147 'connect':175 'cost':63 'cover':152 'crypto':125 'data':114,127 'decim':74 'descript':193 'detail':182 'difficult':224 'doc':165 'document':157,221 'email':2,14,32,35,197 'email attachment API' 'email-attachments' 'embed':122 'endpoint':26,43,110,132,156,199,209 'exampl':190 'expect':207 'experiment':228 'extrem':162 'financ':123 'gate':108 'header':90 'howev':148 'id':36 'includ':85,113 'infer':117 'infrastructur':129 'input':204 'json':49 'key':77 'lack':219 'limit':80 'list':151 'live':211 'lowpaymentfee email' 'lowpaymentfee.com':28,99 'make':222 'market':126 'micropay':6,18 'micropayment' 'micropayment email attachments' 'minimum':145 'model':142 'network':56 'openapi':186 'page':170 'paid email API' 'paramet':205 'payment':50,89,95 'paywal':41 'per':11,23,66 'platform':100,135 'post':45 'post-endpoint' 'price':141,167 'prompt':177 'proof':96 'provid':29 'rang':104 'rate':79 'readm':169 'render':172 'request':12,24,46,67 'request/response':189 'requir':82 'retriev':1,13 'return':48,201,212 'schema':187 'sentiment':118 'settl':52 'share':136 'simpli':84 'site':160 'spars':163 'specif':34,150 'summar':120 'technic':181 'unit':71 'usd':59 'usdc':58 'usdc-settlement' 'use':57,226 'util':130 'valid':93,214 'via':4,16 'wallet':176 'wide':103 'without':227 'x':88 'x-payment':87 'x402':5,17,40,94,107 'x402 email endpoint' 'x402-gated':106 'x402-payment'","prices":[{"id":"a86426a7-708f-409c-bd3a-6617735d359e","listingId":"cac78abd-e67d-4f6d-b7a4-88e170586616","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/28/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":"2026-04-21T18:32:10.997Z"}],"sources":[{"listingId":"cac78abd-e67d-4f6d-b7a4-88e170586616","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/28/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:10.997Z","lastSeenAt":"2026-04-22T10:32:39.186Z"}],"details":{"listingId":"cac78abd-e67d-4f6d-b7a4-88e170586616","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/28/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":"Endpoint returns 402 with x402 challenge advertising USDC on Base at maxAmountRequired 20000","source_url":"https://lowpaymentfee.com/api/v1/emails/28/attachments"},{"claim":"Platform advertises $0.02/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 network","source_url":"https://lowpaymentfee.com/api/v1/emails/28/attachments"},{"claim":"Docs, API, pricing, and README pages render only 'Connect wallet' with no further content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Retrieving email attachments programmatically via micropayment","Agent-driven access to email data without API key management","Pay-per-request email attachment retrieval on Base L2"],"bestFor":["Agents needing on-demand email attachment access without subscriptions","Developers experimenting with x402 payment protocol integrations","Scenarios requiring keyless, pay-per-use API access"],"notFor":["Bulk email processing requiring high throughput at low cost","Users who need detailed API documentation before integrating","Non-crypto workflows that cannot settle payments on Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:21.49Z"},"updatedAt":"2026-04-22T10:32:39.186Z"}}