import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import type { Resend } from 'resend';
import { z } from 'zod';
export function addEmailTools(
server: McpServer,
resend: Resend,
{
senderEmailAddress,
replierEmailAddresses,
}: {
senderEmailAddress?: string;
replierEmailAddresses: string[];
},
) {
server.tool(
'send-email',
'Send an email using Resend',
{
to: z.string().email().describe('Recipient email address'),
subject: z.string().describe('Email subject line'),
text: z.string().describe('Plain text email content'),
html: z
.string()
.optional()
.describe(
'HTML email content. When provided, the plain text argument MUST be provided as well.',
),
cc: z
.string()
.email()
.array()
.optional()
.describe(
'Optional array of CC email addresses. You MUST ask the user for this parameter. Under no circumstance provide it yourself',
),
bcc: z
.string()
.email()
.array()
.optional()
.describe(
'Optional array of BCC email addresses. You MUST ask the user for this parameter. Under no circumstance provide it yourself',
),
scheduledAt: z
.string()
.optional()
.describe(
"Optional parameter to schedule the email. This uses natural language. Examples would be 'tomorrow at 10am' or 'in 2 hours' or 'next day at 9am PST' or 'Friday at 3pm ET'.",
),
// If sender email address is not provided, the tool requires it as an argument
...(!senderEmailAddress
? {
from: z
.string()
.email()
.nonempty()
.describe(
'Sender email address. You MUST ask the user for this parameter. Under no circumstance provide it yourself',
),
}
: {}),
...(replierEmailAddresses.length === 0
? {
replyTo: z
.string()
.email()
.array()
.optional()
.describe(
'Optional email addresses for the email readers to reply to. You MUST ask the user for this parameter. Under no circumstance provide it yourself',
),
}
: {}),
},
async ({
from,
to,
subject,
text,
html,
replyTo,
scheduledAt,
cc,
bcc,
}) => {
const fromEmailAddress = from ?? senderEmailAddress;
const replyToEmailAddresses = replyTo ?? replierEmailAddresses;
// Type check on from, since "from" is optionally included in the arguments schema
// This should never happen.
if (typeof fromEmailAddress !== 'string') {
throw new Error('from argument must be provided.');
}
// Similar type check for "reply-to" email addresses.
if (
typeof replyToEmailAddresses !== 'string' &&
!Array.isArray(replyToEmailAddresses)
) {
throw new Error('replyTo argument must be provided.');
}
console.error(`Debug - Sending email with from: ${fromEmailAddress}`);
// Explicitly structure the request with all parameters to ensure they're passed correctly
const emailRequest: {
to: string;
subject: string;
text: string;
from: string;
replyTo: string | string[];
html?: string;
scheduledAt?: string;
cc?: string[];
bcc?: string[];
} = {
to,
subject,
text,
from: fromEmailAddress,
replyTo: replyToEmailAddresses,
};
// Add optional parameters conditionally
if (html) {
emailRequest.html = html;
}
if (scheduledAt) {
emailRequest.scheduledAt = scheduledAt;
}
if (cc) {
emailRequest.cc = cc;
}
if (bcc) {
emailRequest.bcc = bcc;
}
console.error(`Email request: ${JSON.stringify(emailRequest)}`);
const response = await resend.emails.send(emailRequest);
if (response.error) {
throw new Error(
`Email failed to send: ${JSON.stringify(response.error)}`,
);
}
return {
content: [
{
type: 'text',
text: `Email sent successfully! ${JSON.stringify(response.data)}`,
},
],
};
},
);
}
