x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys required.
What it does
This endpoint at lowpaymentfee.com exposes a portfolio resource at `/api/v1/portfolios/31` behind an x402 payment wall. It accepts POST requests and returns JSON. Payment is settled on the Base network using USDC (contract 0x8335…2913) with an exact-scheme challenge requiring up to 20,000 base units (i.e., $0.02 given USDC's 6 decimals).
The provider, lowpaymentfee.com, hosts a broader catalog of x402-gated APIs spanning data & analytics, AI/ML inference (sentiment, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are advertised at $0.02 per request with no API keys, no rate limits, and instant access.
The specific `/api/v1/portfolios/31` endpoint is listed under "Premium API Access" but no further documentation describes the request body schema, response fields, or the nature of the portfolio data returned. The docs, pricing, and API pages on the site all render only a "Connect wallet" prompt with no additional content. Because of this, the exact purpose and output of this particular endpoint remain unclear — it could be financial portfolio data, an analytics portfolio, or something else entirely. Treat this listing as a stub until richer documentation is available.
Capabilities
Use cases
- —Fetching portfolio data on-demand with per-request USDC micropayments
- —Agent-driven access to a paid data resource without managing API keys
- —Integrating x402 payment flows into automated workflows
Fit
Best for
- —Developers experimenting with x402 pay-per-call protocols
- —Agents that need keyless, on-demand access to paid endpoints
- —Users who prefer crypto micropayments over subscription billing
Not for
- —Users who need detailed documentation or guaranteed SLAs before integrating
- —High-volume consumers who would benefit from bulk/subscription pricing
- —Anyone without a Base-network USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/31 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live (402 challenge captured) and pricing is clear ($0.02 USDC on Base), but there is no documentation for the request body, response schema, or what 'portfolios/31' actually returns. Docs pages render only a wallet-connect prompt. This is effectively a stub listing.
Warnings
- —No documentation available — docs, pricing, and API pages all show only 'Connect wallet'
- —Request body schema is unknown; no OpenAPI spec provided
- —Response schema and fields are undocumented
- —The purpose of '/api/v1/portfolios/31' is not explained anywhere in the crawled material
- —Cannot verify what data is actually returned without making a paid request
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units in USDC on Base networkhttps://lowpaymentfee.com/api/v1/portfolios/31
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/portfolios/31
- —The site hosts APIs across data & analytics, AI/ML, finance & Web3, and infrastructure categorieshttps://lowpaymentfee.com