x402-gated card-transactions endpoint on Base, pay $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com exposes a POST resource at `/api/v1/cards/90/transactions` behind an x402 payment challenge. The endpoint is live and returns a 402 with an exact-scheme challenge requiring USDC payment on the Base network. The maximum amount required per call is 20,000 base units of USDC (6 decimals), which equals $0.02 USD per request. Payment is sent to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the USDC contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` on Base.
The provider's landing page advertises a broad catalog of x402-gated APIs spanning data & analytics, AI/ML inference, finance/Web3, and infrastructure utilities — all priced at $0.02 per request with no API keys, no rate limits, and instant access. However, the specific endpoint listed here (`/api/v1/cards/90/transactions`) is labeled only as "Premium API Access" and does not appear in the provider's publicly listed catalog. There is no documentation, request/response schema, or usage examples available for this particular endpoint. The docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no additional content.
Because the endpoint's purpose is unclear — the path suggests card transaction data but no schema or documentation confirms this — agents should treat this as an opaque POST endpoint with unknown input/output contracts. The x402 challenge itself is well-formed and the endpoint is confirmed live.
Capabilities
Use cases
- —Fetching card transaction data (speculative, based on URL path)
- —Demonstrating x402 payment flow integration on Base
- —Pay-per-request API consumption without API key management
Fit
Best for
- —Developers experimenting with x402 payment protocol on Base
- —Agents that can settle USDC micropayments on Base L2
- —Use cases needing keyless, pay-per-call API access
Not for
- —Production use requiring documented request/response schemas
- —Users who need free or fiat-settled API access
- —Anyone needing detailed API documentation before integration
Quick start
# 1. Send a POST to get the 402 challenge
curl -X POST https://lowpaymentfee.com/api/v1/cards/90/transactions
# Returns 402 with x402 payment challenge
# 2. Construct X-PAYMENT header with USDC payment proof (20000 base units = $0.02)
# 3. Resend POST with X-PAYMENT header to access the resourceExample
Response
{
"error": "X-PAYMENT header is required",
"accepts": [
{
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"extra": {
"name": "USD Coin",
"version": "2"
},
"payTo": "0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3",
"scheme": "exact",
"network": "base",
"mimeType": "application/json",
"resource": "https://lowpaymentfee.com/api/v1/cards/90/transactions",
"description": "Premium API Access",
"maxAmountRequired": "20000",
"maxTimeoutSeconds": 300
}
],
"x402Version": 1
}Endpoint
Quality
The x402 challenge is well-formed and the endpoint is confirmed live, but there is no documentation, no request/response schema, and the endpoint's actual purpose is unclear. The specific path does not appear in the provider's public catalog. Effectively a stub listing.
Warnings
- —No documentation available for this specific endpoint — docs/pricing/README pages only show 'Connect wallet'
- —Endpoint path /api/v1/cards/90/transactions does not appear in the provider's public API catalog
- —No request or response schema available; input/output contract is unknown
- —The hardcoded '90' in the path suggests a resource-specific endpoint but its meaning is undocumented
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/cards/90/transactions
- —The provider advertises all APIs at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/cards/90/transactions
- —Docs, API, pricing, and README pages render only a 'Connect wallet' prompthttps://lowpaymentfee.com/docs