Vercel AI SDK

npm install ai @ai-sdk/openai zod

import { generateText, tool } from "ai";
import { openai } from "@ai-sdk/openai";
import { z } from "zod";

const API = "https://api.sentvia.ai/v1";
const H = { Authorization: `Bearer ${process.env.SENTVIA_KEY}`, "Content-Type": "application/json" };
const call = (path: string, body?: unknown, method = "POST") =>
  fetch(`${API}${path}`, { method, headers: H, body: body && JSON.stringify(body) }).then((r) => r.json());

const tools = {
  sendEmail: tool({
    description: "Send an email from an inbox.",
    parameters: z.object({ inboxId: z.string(), to: z.string(), subject: z.string(), body: z.string() }),
    execute: ({ inboxId, to, subject, body }) =>
      call("/messages", { inbox_id: inboxId, to: [to], subject, text: body }),
  }),
  checkInbox: tool({
    description: "List recent messages in an inbox.",
    parameters: z.object({ inboxId: z.string() }),
    execute: ({ inboxId }) => call(`/messages?inbox_id=${inboxId}&limit=10`, undefined, "GET"),
  }),
};

const { text } = await generateText({
  model: openai("gpt-4o"),
  tools,
  maxSteps: 5,                 // let the model chain tool calls
  prompt: "Check inbox inb_123 and summarise anything that needs a reply.",
});
console.log(text);