{"id":"edc15a1c-8e3b-4c9c-8839-f81c1800149d","shortId":"G6f5F9","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 for email ID 5) 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 suite of x402-gated APIs spanning data & analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are priced at $0.02 per request and settle on the Base network using USDC.\n\nDocumentation is extremely sparse — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available. The specific functionality of this email attachments endpoint (what input it expects, what attachment data it returns) is not documented beyond the endpoint path and the x402 challenge metadata.","tags":[],"capabilities":["x402-payment","usdc-base","email-attachments","json-response","per-request-billing","no-api-key"],"categories":["email","storage"],"synonyms":["email attachment API","x402 email endpoint","pay-per-request email","Base USDC API","micropayment email access","lowpaymentfee API"],"warnings":["No API documentation available — docs, pricing, and README pages all show only 'Connect wallet'","No OpenAPI or request/response schema provided","Endpoint path references a specific email ID (5), suggesting it may be a demo or placeholder rather than a general-purpose API","No examples of expected request body or response format"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/5/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/5/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 (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no documentation, no OpenAPI spec, no request/response schema, and no examples. The endpoint path suggests a hardcoded email ID (5), which is unusual and unexplained. Effectively a stub 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'000':67 '20':66 '5':38 '6':71 'Base USDC API' 'accept':45 'access':30 'ai/ml':98 'analysi':101 'analyt':97 'api':76,94,144 'attach':3,15,33,180,187 'avail':173 'base':8,20,58,68,134 'behind':39 'beyond':194 'broader':88 'call':63 'challeng':201 'classif':103 'connect':153 'content':159 'convers':120 'data':96,188 'decim':72 'doc':143 'document':138,168,193 'email':2,14,32,36,179 'email attachment API' 'email-attachments' 'embed':104 'endpoint':26,44,123,181,196 'estim':114 'exampl':172 'exchang':109 'expect':185 'extrem':140 'feed':108 'financ':105 'function':176 'gas':113 'gate':93 'generat':121 'geocod':118 'host':86 'id':37 'infer':99 'infrastructur':116 'input':183 'json':50 'json-response' 'key':77 'limit':79 'lowpaymentfee API' 'lowpaymentfee.com':28,85 'maxamountrequir':64 'metadata':202 'micropay':6,18 'micropayment email access' 'network':59,135 'no-api-key' 'openapi':163 'page':148 'path':197 'pay-per-request email' 'payment':51 'paywal':42 'per':11,23,62,128 'per-request-billing' 'post':46 'price':107,125,145 'prompt':155 'provid':29,84 'quot':112 'rate':78,110 'readm':147 'render':150 'request':12,24,47,129 'request/response':166 'requir':82 'retriev':1,13 'return':49,190 'schema':167 'sentiment':100 'settl':53,131 'span':95 'spars':141 'spec':164 'specif':34,175 'subscript':81 'suit':89 'summar':102 'token':111 'unit':69 'usag':171 'usdc':55,137 'usdc-base' 'use':136 'util':117 'valid':119 'via':4,16 'wallet':154 'web3':106 'x402':5,17,41,92,200 'x402 email endpoint' 'x402-gated':91 'x402-payment'","prices":[{"id":"42bae8a5-47a7-40bb-94d3-6e44d2b8626b","listingId":"edc15a1c-8e3b-4c9c-8839-f81c1800149d","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/5/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":"2026-04-21T18:32:11.177Z"}],"sources":[{"listingId":"edc15a1c-8e3b-4c9c-8839-f81c1800149d","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/5/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:11.177Z","lastSeenAt":"2026-04-22T02:31:49.314Z"}],"details":{"listingId":"edc15a1c-8e3b-4c9c-8839-f81c1800149d","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/5/attachments \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-header>\"","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, maxAmountRequired 20000","source_url":"https://lowpaymentfee.com/api/v1/emails/5/attachments"},{"claim":"All endpoints priced at $0.02 per request with no API keys, no rate limits, 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/5/attachments"}],"useCases":["Retrieving email attachments programmatically with per-call micropayments","Agent-driven workflows that need to fetch email attachment data without API key management","Accessing email data behind a crypto paywall on Base network"],"bestFor":["Developers wanting keyless, pay-per-use email attachment retrieval","AI agents that can settle x402 payments in USDC on Base","Workflows needing on-demand email attachment access without subscriptions"],"notFor":["Bulk email processing requiring high throughput at lower per-unit cost","Users who need detailed API documentation or client SDKs before integrating","Applications requiring non-crypto payment methods"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:21.241Z"},"updatedAt":"2026-04-22T02:31:49.314Z"}}