Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/invoices/29` is listed as "Premium API Access" and returns a standard x402 challenge requiring a maximum of 20,000 base units of USDC (i.e., $0.02) per call. The platform advertises no API keys, no rate limits, and instant access — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader platform groups 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 listed endpoints share the same $0.02/request pricing.
Note that the specific `/api/v1/invoices/29` endpoint's purpose is not well-documented beyond the generic "Premium API Access" label. No OpenAPI schema, request/response examples, or detailed documentation were found in the crawl. The docs, API, pricing, and README pages all returned only a "Connect wallet" prompt with no substantive content. This makes it difficult to determine what data or functionality this particular endpoint returns.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time financial data like token quotes, exchange rates, and gas estimates
- —Running utility operations like geocoding, validation, and data conversion on a per-call basis
- —Integrating pay-per-use data analytics and reporting into agent workflows
Fit
Best for
- —AI agents needing low-friction, keyless API access to diverse endpoints
- —Developers who want pay-as-you-go pricing without subscriptions or rate limits
- —Crypto-native applications already operating on the Base network with USDC
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscription plans
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/29 \
-H "X-PAYMENT: <x402-payment-proof>" \
-H "Content-Type: application/json"Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no OpenAPI schema, no request/response examples, and no meaningful documentation — the docs/pricing/README pages all render only a wallet-connect prompt. The specific purpose of /api/v1/invoices/29 is unknown beyond the generic label.
Warnings
- —No OpenAPI or schema documentation available for this endpoint
- —The docs, pricing, API, and README pages contain no substantive content (only 'Connect wallet')
- —The specific functionality of /api/v1/invoices/29 ('Premium API Access') is not described anywhere
- —Cannot verify what data or service this endpoint actually returns without making a paid request
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/invoices/29
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers endpoints in Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/invoices/29