x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys required.
What it does
This endpoint at `/api/v1/portfolios/51` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. The specific `/portfolios/51` resource is listed under "Premium API Access" but its exact data payload is not documented beyond the generic description.
The endpoint is live and returns a valid x402 challenge (HTTP 402) requesting payment of 20,000 base units of USDC (0x8335…2913) on the Base network, which equals $0.02 per request (USDC uses 6 decimals). Payment is sent to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using the "exact" payment scheme. The response MIME type is `application/json` and the method is POST. No API keys, rate limits, or subscriptions are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
Documentation is extremely sparse. The landing page lists many endpoints at $0.02 each across categories (analytics, AI, finance, utilities), but the docs, pricing, API, and README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema, and no usage examples available. The actual data returned by `/api/v1/portfolios/51` is unknown from the available material.
Capabilities
Use cases
- —Accessing portfolio data via a single paid API call without needing an account or API key
- —Integrating pay-per-request data endpoints into autonomous agent workflows
- —Programmatic retrieval of portfolio information settled on-chain via USDC on Base
Fit
Best for
- —Agents or scripts that need keyless, on-demand API access with crypto micropayments
- —Developers experimenting with x402-protocol pay-per-request patterns
- —Use cases where avoiding subscription commitments and rate limits is valuable
Not for
- —Users who need detailed documentation or guaranteed SLAs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscription plans
- —Anyone without access to USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/51 \
-H "X-PAYMENT: <x402-payment-proof>" \
-H "Content-Type: application/json"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but documentation is essentially nonexistent — no OpenAPI spec, no request/response schemas, no examples, and no explanation of what data the /portfolios/51 resource actually returns. The docs pages render only a wallet-connect prompt. This is effectively a stub listing.
Warnings
- —No documentation available — docs, pricing, API, and README pages all show only 'Connect wallet' with no content
- —No OpenAPI or schema definition for request or response payloads
- —The actual data returned by /api/v1/portfolios/51 is completely undocumented
- —Cannot verify what 'Premium API Access' actually provides beyond a JSON response
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/portfolios/51
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers APIs across Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com