{"id":"b470518f-d2ed-4d7a-80d2-b5ecf37dfed4","shortId":"M8FRHK","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 51) 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 catalog of x402-gated APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/Web3 data (price feeds, exchange rates, gas estimates), and infrastructure utilities (geocoding, validation, conversion). All endpoints share the same $0.02/request pricing model and settle on Base via USDC. However, the specific endpoint listed here — `/api/v1/emails/51/attachments` — is not featured on the provider's public landing page, and no documentation exists describing its request schema, expected input parameters, or response format. The crawled docs, pricing, and API pages returned only a \"Connect wallet\" prompt with no further content.\n\nBecause there is no OpenAPI spec, no request/response examples, and no documentation for this particular email-attachments endpoint, its exact functionality and expected POST body remain unclear. The endpoint is confirmed live (402 challenge captured), but agents should treat this as a low-documentation integration.","tags":[],"capabilities":["x402-payment","usdc-base","email-attachments","micropayment","pay-per-request","json-response"],"categories":["email","storage"],"synonyms":["email attachment API","x402 email endpoint","USDC micropayment API","Base network API","pay-per-call email","lowpaymentfee email"],"warnings":["No documentation or OpenAPI schema available for this endpoint","The /api/v1/emails/51/attachments path is not listed on the provider's public API catalog — its purpose and expected inputs are unknown","Crawled docs/pricing/API pages returned only 'Connect wallet' with no usable content","Request body schema and response format are completely undocumented"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/51/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/51/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 with clear pricing, but there is no documentation, no OpenAPI spec, no request/response examples, and the specific email-attachments endpoint is not listed on the provider's own landing page. Functionality is essentially 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'/request':124 '0.02':10,22,60,72,123 '000':66 '20':65 '402':214 '51':37 '6':70 'Base network API' 'USDC micropayment API' 'accept':44 'access':30 'agent':218 'ai/ml':97 'analysi':100 'analyt':96 'api':75,93,169 'attach':3,15,33,198 'base':8,20,57,67,130 'behind':38 'bodi':206 'broader':87 'call':62 'captur':216 'catalog':88 'challeng':215 'classif':102 'confirm':212 'connect':174 'content':180 'convers':117 'crawl':165 'data':95,105 'decim':71 'describ':154 'doc':166 'document':152,192,226 'email':2,14,32,35,197 'email attachment API' 'email-attach':196 'email-attachments' 'embed':103 'endpoint':26,43,119,136,199,210 'estim':111 'exact':201 'exampl':189 'exchang':108 'exist':153 'expect':158,204 'featur':142 'feed':107 'finance/web3':104 'format':163 'function':202 'gas':110 'gate':92 'geocod':115 'host':85 'howev':133 'id':36 'infer':98 'infrastructur':113 'input':159 'integr':227 'json':49 'json-response' 'key':76 'land':148 'limit':78 'list':137 'live':213 'low':225 'low-document':224 'lowpaymentfee email' 'lowpaymentfee.com':28,84 'maxamountrequir':63 'micropay':6,18 'micropayment' 'model':126 'network':58 'openapi':185 'page':149,170 'paramet':160 'particular':195 'pay-per-call email' 'pay-per-request' 'payment':50 'paywal':41 'per':11,23,61 'post':45,205 'price':106,125,167 'prompt':176 'provid':29,83,145 'public':147 'rate':77,109 'remain':207 'request':12,24,46,156 'request/response':188 'requir':81 'respons':162 'retriev':1,13 'return':48,171 'schema':157 'sentiment':99 'settl':52,128 'share':120 'span':94 'spec':186 'specif':34,135 'subscript':80 'summar':101 'treat':220 'unclear':208 'unit':68 'usdc':54,132 'usdc-base' 'util':114 'valid':116 'via':4,16,131 'wallet':175 'x402':5,17,40,91 'x402 email endpoint' 'x402-gated':90 'x402-payment'","prices":[{"id":"71f713c7-161a-48fd-9f01-eb0983d60358","listingId":"b470518f-d2ed-4d7a-80d2-b5ecf37dfed4","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/51/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":"2026-04-21T18:32:12.286Z"}],"sources":[{"listingId":"b470518f-d2ed-4d7a-80d2-b5ecf37dfed4","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/51/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:12.286Z","lastSeenAt":"2026-04-22T02:31:50.480Z"}],"details":{"listingId":"b470518f-d2ed-4d7a-80d2-b5ecf37dfed4","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/51/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 in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/emails/51/attachments"},{"claim":"The provider 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","source_url":"https://lowpaymentfee.com/api/v1/emails/51/attachments"}],"useCases":["Retrieving attachments from a specific email record via programmatic API call","Agent-driven document retrieval behind a micropayment wall","Integrating email attachment access into automated workflows without API key management"],"bestFor":["Agents needing on-demand email attachment retrieval with no subscription","Developers experimenting with x402 payment protocol on Base","Micropayment-gated document access without rate limits"],"notFor":["Bulk email processing or mailbox management","Users who need detailed API documentation before integrating","Non-crypto payment workflows (no fiat/card option available)"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:20.969Z"},"updatedAt":"2026-04-22T02:31:50.480Z"}}