Email Tools for Vercel AI SDK Agents

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

const MULTIMAIL_API = 'https://api.multimail.dev/v1';
const headers = {
  'Authorization': 'Bearer mm_live_your_api_key',
  'Content-Type': 'application/json',
};

const sendEmail = tool({
  description: 'Send an email. In gated_send mode, the email is queued for human approval.',
  parameters: z.object({
    mailbox_id: z.string().describe('The mailbox to send from'),
    to: z.string().email().describe('Recipient email address'),
    subject: z.string().describe('Email subject line'),
    body: z.string().describe('Email body content'),
  }),
  execute: async ({ mailbox_id, to, subject, body }) => {
    const resp = await fetch(`${MULTIMAIL_API}/send`, {
      method: 'POST',
      headers,
      body: JSON.stringify({ mailbox_id, to, subject, body }),
    });
    return resp.json();
  },
});

const checkInbox = tool({
  description: 'Check a mailbox inbox for recent emails.',
  parameters: z.object({
    mailbox_id: z.string().describe('The mailbox to check'),
    limit: z.number().optional().default(10),
  }),
  execute: async ({ mailbox_id, limit }) => {
    const resp = await fetch(
      `${MULTIMAIL_API}/mailboxes/${mailbox_id}/inbox?limit=${limit}`,
      { headers }
    );
    return resp.json();
  },
});

const result = await generateText({
  model: openai('gpt-4o'),
  tools: { sendEmail, checkInbox, replyEmail },
  maxSteps: 5,
  system: `You are an email assistant. You can send emails, check inboxes,
    and reply to messages. The mailbox uses gated_send mode, so all
    outgoing emails are queued for human approval before delivery.
    Mailbox ID: mbx_main`,
  prompt: 'Check my inbox and draft a reply to any unanswered emails.',
});

console.log(result.text);

"cm">// app/api/chat/route.ts
import { streamText } from 'ai';
import { openai } from '@ai-sdk/openai';

export async function POST(req: Request) {
  const { messages } = await req.json();

  const result = streamText({
    model: openai('gpt-4o'),
    tools: { sendEmail, checkInbox, replyEmail, getThread },
    maxSteps: 5,
    system: `You are an email assistant for the user's MultiMail account.
      Always confirm the recipient and subject before sending.
      The mailbox uses gated_send mode — emails need approval.`,
    messages,
  });

  return result.toDataStreamResponse();
}

const getThread = tool({
  description: 'Get all messages in an email thread for context.',
  parameters: z.object({
    thread_id: z.string().describe('The thread ID to retrieve'),
  }),
  execute: async ({ thread_id }) => {
    const resp = await fetch(
      `${MULTIMAIL_API}/threads/${thread_id}`,
      { headers }
    );
    return resp.json();
  },
});

const replyEmail = tool({
  description: 'Reply to an email within its thread.',
  parameters: z.object({
    message_id: z.string().describe('The message ID to reply to'),
    body: z.string().describe('Reply body content'),
  }),
  execute: async ({ message_id, body }) => {
    const resp = await fetch(`${MULTIMAIL_API}/reply`, {
      method: 'POST',
      headers,
      body: JSON.stringify({ message_id, body }),
    });
    return resp.json();
  },
});