Pay-per-call API suite 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 collection of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and general utility services. Every endpoint is priced at $0.02 per request, paid in USDC on the Base network via the x402 payment protocol. There are no API keys, no rate limits, and no minimum commitments — callers simply attach an X-PAYMENT header to each request.
The specific endpoint at `/api/v1/invoices/20` is listed as "Premium API Access" and returns an x402 challenge requesting up to 20,000 base units of USDC (0.02 USD, since USDC uses 6 decimals) on Base. The payment is settled to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` with a 300-second timeout. The broader platform advertises categories including metrics, reports, data export, insights, sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, token quotes, gas estimates, geocoding, validation, conversion, and generation — all at the same $0.02 price point.
Documentation is extremely thin: 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 crawl. The endpoint is confirmed live (402 challenge captured), but the actual behavior behind each API path is unverifiable from the available material.
Capabilities
Use cases
- —Agent-driven data retrieval without API key management
- —On-demand AI inference (sentiment, summarization, classification, embeddings) paid per call
- —Fetching real-time crypto prices, gas estimates, and exchange rates via micropayment
- —Geocoding and data conversion utilities with zero setup
Fit
Best for
- —AI agents needing keyless, pay-as-you-go API access
- —Developers prototyping with low-cost per-request pricing on Base
- —Web3-native applications that already hold USDC on Base
Not for
- —High-volume production workloads needing SLAs or guaranteed uptime
- —Users who need detailed API documentation or response schema guarantees before integrating
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/20 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is confirmed live with a valid x402 402 challenge and clear pricing ($0.02 USDC on Base). However, documentation is essentially absent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response schemas, and no examples for any endpoint. The actual functionality behind the listed paths is unverifiable.
Warnings
- —Documentation pages (/docs, /api, /pricing, /README) return no useful content beyond 'Connect wallet'
- —No OpenAPI or schema documentation available — request and response formats are unknown
- —The breadth of advertised capabilities (AI, finance, analytics, utilities) cannot be verified from available material
- —No rate limit or uptime guarantees documented
Citations
- —Endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/invoices/20
- —Platform advertises $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/invoices/20
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com