x402 pay-per-call APIs

Problem

Agent tools are often useful as small one-call capabilities, but account setup, subscriptions, and manual checkout do not fit autonomous runtime workflows. x402 lets paid APIs expose HTTP 402 Payment Required and accept programmatic payments.

Primitive402 surfaces

Primitive402 shows how agent tools can be sold as small paid calls. Free /v1 routes are for development and testing. Paid /x402 aliases return HTTP 402 Payment Required until an x402-capable client pays and retries.

The current public beta uses Base Sepolia testnet USDC. Do not treat this as mainnet production billing.

Current paid aliases

curl example

curl -i https://primitive402.dev/x402/v1/safe-fetch-url \
  -H 'content-type: application/json' \
  -d '{"url":"https://example.com","output":"markdown"}'

HTTP 402 Payment Required

TypeScript SDK example

import { createNano402Client } from "@nano402/api/sdk";

const client = createNano402Client({
  baseUrl: "https://primitive402.dev",
  useX402: true,
  paymentHeaders: {
    "x-payment": "<wallet-generated x402 payment header>"
  }
});

const result = await client.safeFetchUrl({
  url: "https://example.com",
  output: "markdown"
});

Example JSON response

{
  "finalUrl": "https://example.com",
  "cleanMarkdown": "# Example Domain...",
  "contentHash": "sha256:...",
  "riskLevel": "low"
}

Useful search terms

x402 pay-per-call APIs, paid APIs for AI agents, HTTP 402 Payment Required, x402 microtools, USDC per-call payments.

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