Your API was designed for humans. Your callers are now agents.

The next decade of API revenue will not come from human signups. It will come from AI agents calling APIs on behalf of their users, often programmatically and without any human in the loop. Those agents cannot use your existing checkout. They cannot fill out a credit card form, cannot create an account, cannot click a confirmation email, cannot remember a password.

What they can do is read a 402 Payment Required response, parse the USDC amount and recipient out of the JSON body, pay on Base, and re-issue the call with proof of payment. That is the entire shape of agent-driven API commerce. The cost model (per-call billing in stablecoin) also fits agent usage shape much better than card-based subscriptions: cards fail at sub-$1 transactions; USDC on Base costs cents in gas; chargebacks do not happen between machines.

Blockchain0x is the bridge. List the routes you want to charge for in a pricing table and mount the x402 adapter. When an unpaid call hits a priced route, the adapter returns a 402 describing exactly what to pay. The agent pays on Base and retries with an X-Payment header; the adapter verifies it and your handler runs. You collect USDC and run your API as before. Nothing about your business logic changes; the billing layer rides alongside.

from flask import Flask
from blockchain0x import Client
from blockchain0x_x402.server import x402_before_request_factory, PricingEntry

sdk = Client()  # reads BLOCKCHAIN0X_API_KEY
app = Flask(__name__)

# Only routes named in the pricing table are gated.
app.before_request(x402_before_request_factory(
    sdk=sdk,
    pricing={
        "POST /api/expensive-operation": PricingEntry(
            amount_usdc="0.50",
            pay_to_address="0xYourAgentWalletAddress",
            payment_request_id="pr_demo",
        ),
    },
))

@app.route("/api/expensive-operation", methods=["POST"])
def expensive_operation():
    return run_the_work()  # only runs after X-Payment verifies

import express from "express";
import { createClient } from "@blockchain0x/node";
import { createX402Middleware } from "@blockchain0x/x402/server/express";

const sdk = createClient({ apiKey: process.env.BLOCKCHAIN0X_API_KEY! });
const app = express();

// Only routes named in the pricing table are gated.
app.use(createX402Middleware({
  sdk,
  pricing: {
    "POST /api/expensive-operation": {
      amountUsdc: "0.50",
      payToAddress: "0xYourAgentWalletAddress",
      paymentRequestId: "pr_demo",
    },
  },
}));

app.post("/api/expensive-operation", async (req, res) => {
  res.json(await runTheWork());  // req.x402Payment holds the verified payment
});

import (
  "net/http"
  x402 "tosh-labs/blockchain0x-x402-go"
)

func main() {
  pricing := map[string]x402.PricingEntry{
    "POST /api/expensive-operation": {
      AmountUSDC:       "0.50",
      PayToAddress:     "0xYourAgentWalletAddress",
      PaymentRequestID: "pr_demo",
    },
  }

  // serverSdk is your Blockchain0x Go SDK client.
  h := x402.Middleware(x402.ServerOptions{Sdk: serverSdk, Pricing: pricing})(
    http.HandlerFunc(expensiveOperation))
  http.Handle("/api/expensive-operation", h)
  http.ListenAndServe(":8080", nil)
}

We ship server adapters for Express and Fastify (Node), ASGI (Starlette and FastAPI) and Flask (Python), and Go's net/http. For other frameworks, the 402 body and X-Payment header are plain HTTP that the wire helpers in @blockchain0x/x402 build and parse - hand-write the check in your stack's idiom. Ruby and JVM x402 packages are published for the client side.

Pro for early traffic. Business when audit logs become a requirement.

API providers almost always start on Pro from day one: Free is read-only, and the x402 adapter needs the API access to verify and settle payments plus webhooks to track them. High-traffic APIs cross into Business territory as monthly volume climbs. See the pricing page for the exact per-agent cost and where the tiers sit.

• Free: useful only for the dashboard and metadata exploration. Read-only, so the adapter cannot settle payments.
• Pro: default for live API monetization. Full API access, webhooks, exports.
• Business: when you need audit logs for compliance, or higher API rate limits.