Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that provides a collection of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and general utility services. All endpoints are paid per-request using USDC on the Base network via the x402 protocol — no API keys, no rate limits, and no subscriptions required.
The specific endpoint at `/api/v1/invoices/9` is listed as "Premium API Access" and accepts POST requests. Its x402 challenge advertises a maximum cost of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 per call (USDC uses 6 decimals). The broader platform lists roughly 16 endpoints across 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 at the same $0.02 price point.
Documentation 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 from the crawled material. The endpoint is confirmed live (returns a proper 402 challenge), but without documentation it is difficult to know what request body to send or what response to expect.
Capabilities
Use cases
- —Accessing AI inference (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time financial data and crypto gas estimates with per-call USDC payments
- —Running data analytics queries and exporting data on demand
- —Using utility services like geocoding, validation, and conversion via micropayments
Fit
Best for
- —Developers who want zero-signup, pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing low-cost, no-commitment access to diverse API endpoints
Not for
- —Users who need detailed API documentation or guaranteed SLAs
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Developers without USDC on Base or unfamiliar with x402 payment flows
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/9 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-header>" \
-d '{}'Endpoint
Quality
The endpoint is confirmed live with a valid x402 402 challenge and clear pricing ($0.02 USDC on Base). However, documentation is effectively nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response schema, and no examples. The purpose of the specific /invoices/9 endpoint is unclear beyond the generic 'Premium API Access' label.
Warnings
- —Documentation pages (docs, API, pricing, README) all render only 'Connect wallet' with no usable content
- —No OpenAPI or schema documentation available for any endpoint
- —The specific purpose and expected request/response format of /api/v1/invoices/9 is undocumented
- —The broader platform lists many endpoints but none have documented schemas or examples
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/invoices/9
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/invoices/9
- —Platform lists 16 endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories all at $0.02/requesthttps://lowpaymentfee.com
- —No API keys, no rate limits, instant access, Base networkhttps://lowpaymentfee.com
- —Docs, API, pricing, and README pages show only 'Connect wallet'https://lowpaymentfee.com/docs