{"id":"b8c79193-9f8d-4959-89a9-10dd3ded5ceb","shortId":"aMxvA3","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 43) behind an x402 paywall. The endpoint accepts POST requests and returns application/json responses. 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 hosts a variety of x402-gated APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/crypto data feeds, and utility services, all priced uniformly at $0.02 per call. However, this specific listing covers only the `/api/v1/emails/43/attachments` endpoint. The purpose and content of \"email 43\" attachments is not documented — the endpoint appears to be a demonstration or specific data resource rather than a general-purpose email API.\n\nThe endpoint is live and returns a proper x402 challenge (HTTP 402) with version 1 of the protocol. Payment is made to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using USDC contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base. The maximum timeout for payment settlement is 300 seconds.","tags":[],"capabilities":["x402-payment","email-attachments","base-network","usdc-settlement","micropayment","json-response","post-method"],"categories":["data","email"],"synonyms":["email attachment API","x402 email endpoint","pay-per-request email","lowpaymentfee API","micropayment email access","Base USDC API"],"warnings":["No documentation available for this specific endpoint — purpose of 'email 43 attachments' is unknown","No request body schema or response schema documented","Docs, pricing, API, and README pages all render only a 'Connect wallet' prompt with no useful content","This appears to be a fixed resource endpoint (email ID 43) rather than a parameterized email API"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/43/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/43/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live and returns a valid x402 challenge, but there is no documentation on what the email attachments endpoint actually returns, no request/response schema, and no examples. The crawled docs/pricing/API pages are empty beyond a wallet connect prompt. The endpoint path suggests a very specific resource (email 43) rather than a general-purpose API, and its purpose is 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'0.02':10,22,66,130 '000':70 '0x1a2b13e97f5f837c8f9fa1f95a1484b7c70d85f3':195 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':199 '1':186 '20':69 '300':209 '402':183 '43':37,148 '6':74 'Base USDC API' 'accept':44 'access':30 'address':194 'ai/ml':113 'analysi':116 'analyt':112 'api':77,109,171 'appear':155 'application/json':49 'attach':3,15,33,149 'base':8,20,56,71,201 'base-network' 'behind':38 'broader':99 'call':132 'caller':84 'challeng':181 'classif':118 'coin':61 'content':145 'contract':198 'cost':64 'cover':137 'data':111,121,162 'decim':75 'demonstr':159 'document':152 'email':2,14,32,35,147,170 'email attachment API' 'email-attachments' 'embed':119 'endpoint':26,43,141,154,173 'feed':122 'finance/crypto':120 'gate':108 'general':168 'general-purpos':167 'header':91 'host':102 'howev':133 'http':182 'id':36 'includ':86 'infer':114 'json-response' 'key':78 'limit':81 'list':136 'live':175 'lowpaymentfee API' 'lowpaymentfee.com':28,100 'made':192 'maximum':203 'micropay':6,18 'micropayment' 'micropayment email access' 'network':57 'pay-per-request email' 'payment':51,90,96,190,206 'paywal':41 'per':11,23,67,131 'platform':101 'post':45 'post-method' 'price':127 'proof':97 'proper':179 'protocol':189 'provid':29 'purpos':143,169 'rate':80 'rather':164 'request':12,24,46,68 'requir':83 'resourc':163 'respons':50 'retriev':1,13 'return':48,177 'second':210 'sentiment':115 'servic':125 'settl':53 'settlement':207 'simpli':85 'span':110 'specif':34,135,161 'summar':117 'timeout':204 'uniform':128 'unit':72 'usd':60 'usdc':59,197 'usdc-settlement' 'use':58,196 'util':124 'valid':94 'varieti':104 'version':185 'via':4,16 'x':89 'x-payment':88 'x402':5,17,40,95,107,180 'x402 email endpoint' 'x402-gated':106 'x402-payment'","prices":[{"id":"fdcca438-20ef-4699-a7c4-d8ef3b59700d","listingId":"b8c79193-9f8d-4959-89a9-10dd3ded5ceb","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/43/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":"2026-04-21T18:32:11.198Z"}],"sources":[{"listingId":"b8c79193-9f8d-4959-89a9-10dd3ded5ceb","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/43/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:11.198Z","lastSeenAt":"2026-04-22T09:02:00.898Z"}],"details":{"listingId":"b8c79193-9f8d-4959-89a9-10dd3ded5ceb","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/43/attachments \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"Endpoint returns HTTP 402 with x402 version 1 challenge requesting USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/43/attachments"},{"claim":"Price is $0.02 per request across all APIs on the platform","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/emails/43/attachments"},{"claim":"No API keys, no rate limits, instant access advertised","source_url":"https://lowpaymentfee.com"}],"useCases":["Retrieving attachments from a specific email resource behind a micropayment wall","Demonstrating x402 protocol payment flows for agent-to-API transactions","Programmatic access to email attachment data without API key registration"],"bestFor":["Developers experimenting with x402 micropayment protocol on Base","Agents that need to fetch email attachment data with per-call payment","Low-friction API access without signup or API key management"],"notFor":["General-purpose email or mailbox access — this is a single fixed email resource","High-volume bulk email processing where per-request fees would accumulate","Users who need detailed documentation or schema definitions before integrating"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:21.241Z"},"updatedAt":"2026-04-22T09:02:00.898Z"}}