Give a Vercel AI SDK agent a tool it pays for per call.

// tools/apiosk.ts
// The paying client plus the first tool. Typechecks against ai 7,
// @x402/axios 2, @x402/evm 2, viem 2, zod 4.

import axios from "axios";
import { wrapAxiosWithPaymentFromConfig } from "@x402/axios";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";
import { tool } from "ai";
import { z } from "zod";

const account = privateKeyToAccount(process.env.WALLET_PRIVATE_KEY as `0x${string}`);

// One client for every endpoint on the gateway. Base mainnet is the CAIP-2 id
// "eip155:8453". The interceptor answers the 402, signs the USDC payment and
// retries the request, so execute() below only ever sees the data.
export const apiosk = wrapAxiosWithPaymentFromConfig(
  axios.create({ baseURL: "https://gateway.apiosk.com" }),
  { schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }] },
);

// inputSchema, not parameters. The field was renamed in AI SDK v5 and is
// required in v7, so there is no tool() overload that matches `parameters`:
// tsc rejects the call outright rather than building a tool with no schema.
export const convertCurrency = tool({
  description: "Convert an amount between two currencies using live FX rates.",
  inputSchema: z.object({
    from: z.string().describe("ISO currency code to convert from, e.g. EUR"),
    to: z.string().describe("ISO currency code to convert to, e.g. USD"),
    amount: z.number().positive(),
  }),
  execute: async ({ from, to, amount }) => {
    const { data } = await apiosk.get("/v1/fx/convert", {
      params: { from, to, amount },
    });
    return data;
  },
});

// tools/verify-email.ts
// A second job on the same client. Nothing about the payment path changes.

import { tool } from "ai";
import { z } from "zod";
import { apiosk } from "./apiosk";

export const verifyEmail = tool({
  description: "Check whether an email address is deliverable.",
  inputSchema: z.object({
    email: z.string().describe("The address to check, e.g. ada@example.com"),
  }),
  execute: async ({ email }) => {
    const { data } = await apiosk.get("/v1/email/verify", { params: { email } });
    return data;
  },
});

// agent.ts
// Run with: npx tsx agent.ts

import { anthropic } from "@ai-sdk/anthropic";
import { generateText, isStepCount } from "ai";
import { convertCurrency } from "./tools/apiosk";
import { verifyEmail } from "./tools/verify-email";

const result = await generateText({
  model: anthropic("claude-opus-5"),
  tools: { convertCurrency, verifyEmail },
  // stopWhen replaces maxSteps. isStepCount is the v7 name; stepCountIs is
  // still exported as an alias. Five steps is five tool round trips at most.
  stopWhen: isStepCount(5),
  prompt: "What is 250 EUR in USD right now?",
});

console.log(result.text);

// Each paid call is in the step record:
// result.steps.flatMap((step) => step.toolResults);