x402-gated API suite on Base: analytics, AI, finance, and utility endpoints at $0.02/request via USDC.
What it does
lowpaymentfee.com hosts a collection of pay-per-call API endpoints gated by the x402 protocol on the Base network. The specific endpoint `/api/v1/carts/97` is listed as "Premium API Access" and requires a payment of up to 20,000 units of USDC (asset 0x8335…2913, which has 6 decimals, so this equals $0.02) per request. Payment is made via an `X-PAYMENT` header using the x402 "exact" scheme, settling on-chain to address 0x1A2B…85F3.
The broader platform advertises four categories of APIs: 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 endpoints are listed at $0.02 per request with no API keys, no rate limits, and no minimum commitments.
Documentation is extremely sparse — the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawl. The endpoint at `/api/v1/carts/97` is confirmed live (returns a proper 402 challenge), but what it actually returns upon successful payment is unknown. The "carts/97" path does not correspond to any of the advertised API categories, adding further ambiguity about this specific endpoint's purpose.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key registration
- —Fetching real-time financial data such as token quotes, exchange rates, and gas estimates on a per-call basis
- —Running data analytics queries and exporting reports with per-request USDC micropayments
- —Using utility services like geocoding and data validation via crypto-native pay-per-use
Fit
Best for
- —Agents or developers who want keyless, pay-per-call API access settled in USDC on Base
- —Crypto-native applications that prefer on-chain micropayments over subscription billing
- —Quick prototyping where avoiding API key signup and rate limits is valuable
Not for
- —High-volume production workloads where $0.02/request adds up and bulk pricing is needed
- —Users who need detailed API documentation, SLAs, or guaranteed uptime
- —Applications requiring non-crypto payment methods
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/97 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is confirmed live with a valid x402 402 challenge, but documentation is essentially nonexistent — every doc page shows only 'Connect wallet'. There is no OpenAPI spec, no request/response schema, no examples, and the specific endpoint path '/api/v1/carts/97' does not match any of the advertised API categories, making its purpose unclear. Pricing is inferrable from the challenge but little else is verifiable.
Warnings
- —Documentation pages (/docs, /api, /pricing, /README) all return only 'Connect wallet' with no usable content
- —No OpenAPI or schema documentation available
- —The endpoint path /api/v1/carts/97 does not correspond to any of the advertised API categories — its actual functionality is unknown
- —No request body schema or response schema documented; callers cannot know what to send or expect back
- —Platform appears to be a generic x402 demo or storefront; actual API functionality behind payment wall is unverified
Citations
- —Endpoint returns 402 with x402 challenge requiring USDC payment on Base networkhttps://lowpaymentfee.com/api/v1/carts/97
- —Platform advertises APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories at $0.02/requesthttps://lowpaymentfee.com
- —No API keys, no rate limits, instant access, Base networkhttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/carts/97