x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-protocol API marketplace that gates access to a variety of endpoints behind per-request micropayments settled in USDC on the Base network. The specific endpoint at `/api/v1/carts/41` is listed as "Premium API Access" and requires a maximum payment of 20,000 base units of USDC (0.02 USD, since USDC uses 6 decimals) per call. No API keys or rate limits are advertised — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader platform organizes its endpoints into four categories: 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 listed at the same $0.02/request price point. The x402 challenge confirms the endpoint is live, accepts POST requests, and settles payments to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using the USDC contract on Base (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913).
Documentation is extremely sparse — the /docs, /pricing, /api, and /README pages all render only a "Connect wallet" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The actual behavior and response format of the `/api/v1/carts/41` endpoint (or any other endpoint) cannot be determined from the available material.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time financial data (prices, exchange rates, gas estimates) via micropayments
- —Running utility operations (geocoding, validation, conversion) on a pay-per-use basis
- —Integrating agent-driven workflows that settle per-call costs in USDC on Base
Fit
Best for
- —Agents or applications that need keyless, pay-per-call API access
- —Developers wanting to avoid subscription commitments for low-volume API usage
- —Crypto-native workflows already operating on the Base network
Not for
- —High-volume production workloads where per-request pricing may add up versus flat-rate plans
- —Users who need detailed API documentation or guaranteed SLAs before integrating
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/41 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The x402 challenge is live and confirms pricing and payment details, but documentation is effectively absent — all doc pages show only 'Connect wallet'. No OpenAPI spec, no request/response schemas, and no examples are available. The purpose of the specific /api/v1/carts/41 endpoint is unclear beyond its title 'Premium API Access'.
Warnings
- —Documentation pages (/docs, /pricing, /api, /README) all render only 'Connect wallet' with no usable content
- —No OpenAPI or schema documentation available for any endpoint
- —The specific purpose and expected input/output of /api/v1/carts/41 is undocumented
- —The broader platform lists many endpoint categories but none have verifiable documentation
Citations
- —All endpoints are priced at $0.02/request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The x402 challenge for /api/v1/carts/41 requires maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/carts/41
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/carts/41
- —Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com