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 marketplace that offers a broad set of endpoints spanning data & analytics, AI & machine learning, finance & Web3, and infrastructure utilities. Every endpoint is priced at $0.02 per request, settled 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 with a valid payment proof to each request.
The specific endpoint at `/api/v1/keys/81` 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 made to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the "exact" scheme with a 300-second timeout. The response MIME type is `application/json`.
The platform advertises additional endpoints including 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. However, no OpenAPI schema, detailed documentation, or example request/response payloads are available for any of these endpoints, so the exact input parameters and output formats remain unknown.
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 billing
- —Geocoding addresses or validating/converting data via utility endpoints paid in USDC
Fit
Best for
- —AI agents that need frictionless, keyless API access with crypto micropayments
- —Developers prototyping with multiple API categories without upfront commitments
- —Web3-native applications already operating on the Base network with USDC
Not for
- —High-volume production workloads where $0.02/request adds up significantly without bulk discounts
- —Users who need detailed API documentation, schemas, or SLAs before integrating
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/keys/81 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>" \
-d '{}'Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, confirming pricing and payment details. However, there is no OpenAPI schema, no documentation beyond a landing page listing, no example requests or responses, and the purpose of the specific `/api/v1/keys/81` endpoint ("Premium API Access") is unclear — it may be a meta-endpoint for key generation rather than a data endpoint. The crawled /api, /pricing, and /README pages returned only a wallet-connect prompt with no useful content.
Warnings
- —No OpenAPI schema or endpoint documentation available
- —The exact purpose and input/output format of /api/v1/keys/81 is unknown — 'Premium API Access' is vague and may be a key-provisioning endpoint rather than a data API
- —Crawled /pricing, /api, and /README pages returned no meaningful content (only 'Connect wallet')
- —No example requests or responses are documented anywhere
- —Cannot verify that the advertised AI, finance, and utility endpoints actually function
Citations
- —The endpoint returns a 402 challenge requesting 20,000 base units of USDC on Base (0.02 USD)https://lowpaymentfee.com/api/v1/keys/81
- —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 across Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —Payment is settled in USDC on the Base network to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3https://lowpaymentfee.com/api/v1/keys/81