x402-gated premium API endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at `/api/v1/cards/87` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. The specific `/api/v1/cards/87` resource is labeled "Premium API Access" but its exact functionality is not documented beyond that title. It accepts HTTP POST requests and returns JSON.
Payment is handled via the x402 protocol on the Base network using USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The maximum amount required per call is 20,000 base units of USDC, which at 6 decimals equals $0.02 USD — consistent with the site's advertised flat $0.02/request pricing across all endpoints. There are no API keys, no rate limits, and no minimum commitments; callers simply attach an `X-PAYMENT` header with a valid x402 payment proof.
The broader lowpaymentfee.com platform advertises endpoints for metrics, reports, data export, insights, sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, token quotes, gas estimates, geocoding, validation, conversion, and generation — all at the same $0.02/request price point. However, documentation is extremely sparse: the docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further technical detail. The specific input/output schema for `/api/v1/cards/87` is unknown.
Capabilities
Use cases
- —Accessing a premium data or utility endpoint with per-request USDC micropayments
- —Integrating x402-compatible agent workflows that pay per API call on Base
- —Testing x402 protocol payment flows against a live endpoint
Fit
Best for
- —Developers experimenting with x402 pay-per-request protocols
- —Agents that need keyless, on-demand API access settled in USDC on Base
- —Low-volume callers who prefer pay-as-you-go over subscriptions
Not for
- —Users who need detailed API documentation or well-defined schemas before integrating
- —High-volume production workloads requiring SLA guarantees or support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/87 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live (402 challenge captured) and pricing is clear ($0.02/request in USDC on Base). However, there is no documentation for the /api/v1/cards/87 resource — no input schema, no output schema, no examples, and no explanation of what 'Premium API Access' actually returns. All doc pages render only 'Connect wallet'.
Warnings
- —The specific functionality of /api/v1/cards/87 ('Premium API Access') is completely undocumented — its purpose, input parameters, and response format are unknown.
- —All documentation pages (docs, API, pricing, README) render only a 'Connect wallet' prompt with no technical content.
- —No OpenAPI spec, no request/response examples, and no error documentation are available.
- —The endpoint path '/api/v1/cards/87' with a numeric ID suggests it may be a specific resource instance rather than a general-purpose API.
Citations
- —The endpoint returns a 402 challenge with x402Version 1, requiring USDC payment on Base networkhttps://lowpaymentfee.com/api/v1/cards/87
- —maxAmountRequired is 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913), equaling $0.02https://lowpaymentfee.com/api/v1/cards/87
- —The platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —Documentation pages render only 'Connect wallet' with no technical contenthttps://lowpaymentfee.com/docs