Pay-per-request API platform on Base (USDC) via x402 — data, AI, finance, and utility endpoints at $0.02/call.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers 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, with no API keys, no rate limits, and no minimum commitments required.
The specific endpoint at `/api/v1/invoices/40` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) on Base. The broader platform advertises a uniform $0.02 per request across all its endpoints. Categories of available APIs include: metrics and reports (Data & Analytics), sentiment analysis, text summarization, classification, and embeddings (AI & ML), price feeds, exchange rates, token quotes, and gas estimates (Finance & Web3), and geocoding, validation, conversion, and generation utilities (Infrastructure).
Documentation is extremely sparse — the /docs, /pricing, /api, 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 (402 challenge captured), but the actual behavior and response format of each API is unknown from the available sources.
Capabilities
Use cases
- —Agents needing on-demand AI inference (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time crypto token quotes, gas estimates, or exchange rates with per-call payment
- —Geocoding or data validation as a utility microservice paid in USDC
- —Exporting data or generating analytics reports on a pay-as-you-go basis
Fit
Best for
- —AI agents that need keyless, pay-per-call access to diverse utility endpoints
- —Developers wanting to avoid subscription commitments for low-volume API usage
- —Web3-native applications that can settle payments in USDC on Base
Not for
- —High-volume production workloads where $0.02/request adds up quickly without bulk discounts
- —Users who need detailed API documentation or guaranteed SLAs before integrating
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/40 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is confirmed live with a valid 402 challenge, and the landing page describes the platform's offerings and pricing. However, there is no OpenAPI spec, no request/response schemas, no documentation beyond a wallet-connect prompt, and no examples. The actual functionality behind '/api/v1/invoices/40' is unclear — it may be a generic or demo endpoint. This is effectively a stub listing.
Warnings
- —No OpenAPI spec or schema documentation available
- —All documentation pages (/docs, /pricing, /api, /README) render only 'Connect wallet' with no content
- —The specific endpoint '/api/v1/invoices/40' is labeled 'Premium API Access' but its actual request/response behavior is undocumented
- —No request body schema or response format is known — integration requires trial and error
- —The platform lists many endpoint categories but none have documented input/output contracts
Citations
- —Uniform pricing of $0.02 per request across all endpoints, no API keys, no rate limitshttps://lowpaymentfee.com
- —Available API categories include Data & Analytics, AI & ML, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —Payment is in USDC on Base network via x402 protocolhttps://lowpaymentfee.com
- —402 challenge returns maxAmountRequired of 20000 base units of USDC (USD Coin, 6 decimals = $0.02)https://lowpaymentfee.com/api/v1/invoices/40