x402-gated premium API access on Base, pay $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com is part of a suite of x402-protocol pay-per-call APIs hosted on the Base network. The specific resource `/api/v1/cards/9` is labeled "Premium API Access" and accepts POST requests gated by an x402 payment challenge. Payment is settled in USDC (contract 0x8335…2913 on Base) at a maximum cost of 20,000 base units, which equals $0.02 per request (USDC uses 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader lowpaymentfee.com platform advertises multiple API categories including Data & Analytics (metrics, reports, data export, insights), AI & Machine Learning (sentiment analysis, text summarization, classification, embeddings), Finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and Infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are uniformly priced at $0.02 per request. However, the specific functionality behind `/api/v1/cards/9` is not documented beyond the generic "Premium API Access" label, so the exact data or service it returns is unclear.
The endpoint is live and returns a well-formed x402 version 1 challenge with a 300-second payment timeout. The output schema indicates it accepts HTTP POST and is discoverable. Documentation pages on the site (docs, pricing, README) appear to require wallet connection and contain no substantive content in the crawl.
Capabilities
Use cases
- —Accessing premium data or services with per-request USDC micropayments on Base
- —Integrating pay-as-you-go API calls into agent workflows without managing API keys
- —Testing x402 protocol payment flows against a live endpoint
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —Agents that need keyless, pay-per-call API access
- —Users who want low-cost micropayment-gated endpoints on Base
Not for
- —Users who need detailed documentation about what the endpoint returns
- —Applications requiring free or subscription-based API access
- —Production workloads that need guaranteed SLAs or support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/9 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but the actual functionality behind '/api/v1/cards/9' is undocumented. No OpenAPI schema, no example responses, and documentation pages are empty (wallet-gated). The listing is essentially a stub with pricing info only.
Warnings
- —The specific functionality of /api/v1/cards/9 is not documented — 'Premium API Access' is a generic label with no details on what data or service is returned.
- —All documentation, pricing, and README pages on the site require wallet connection and returned no useful content in the crawl.
- —No OpenAPI spec, no request/response schema, and no example payloads are available.
- —The endpoint's purpose within the 'cards' namespace is unclear and cannot be inferred from available material.
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 in USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/9
- —All endpoints on the platform are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers APIs across Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/cards/9