resend_send_email

Send emails to recipients with HTML or plain text content, CC/BCC support, reply-to addresses, and custom tracking tags for monitoring.

Instructions

Send a single email to one or more recipients. Supports HTML and plain text content, CC/BCC, reply-to, and custom tags for tracking.

Input Schema

TableJSON Schema

Name	Required	Description
`to`	Yes	Recipient email address(es). Max 50 addresses.
`subject`	Yes	Email subject line
`html`	No	HTML version of the email body
`text`	No	Plain text version. Auto-generated from HTML if omitted.
`cc`	No	CC recipient(s)
`bcc`	No	BCC recipient(s)
`reply_to`	No	Reply-to email address(es)
`tags`	No	Custom metadata tags for tracking (max 50)

Implementation Reference

src/index.ts:75-108 (handler)

Handler for 'resend_send_email' tool: parses arguments with SendEmailRequestSchema, builds Resend email options, sends email, returns success with ID.

case 'resend_send_email': {
  const args = SendEmailRequestSchema.parse(request.params.arguments);

  // Build email options - Resend requires html or text
  const emailOptions: Parameters<typeof resend.emails.send>[0] = {
    from: fromEmail,
    to: args.to,
    subject: args.subject,
    ...(args.html ? { html: args.html } : { text: args.text! }),
    ...(args.cc && { cc: args.cc }),
    ...(args.bcc && { bcc: args.bcc }),
    ...(args.reply_to && { replyTo: args.reply_to }),
    ...(args.tags && { tags: args.tags }),
  };

  const { data, error } = await resend.emails.send(emailOptions);

  if (error) {
    throw new Error(`Failed to send email: ${error.message}`);
  }

  return {
    content: [
      {
        type: 'text',
        text: JSON.stringify({
          success: true,
          id: data?.id,
          message: 'Email sent successfully',
        }),
      },
    ],
  };
}

src/schemas.ts:18-50 (schema)

Input schema (Zod) for the resend_send_email tool defining parameters like to, subject, html/text, cc, bcc, etc.

export const SendEmailRequestSchema = z
  .object({
    to: z
      .union([z.string().email(), z.array(z.string().email()).max(50)])
      .describe('Recipient email address(es). Max 50 addresses.'),
    subject: z.string().describe('Email subject line'),
    html: z.string().optional().describe('HTML version of the email body'),
    text: z
      .string()
      .optional()
      .describe('Plain text version. Auto-generated from HTML if omitted.'),
    cc: z
      .union([z.string().email(), z.array(z.string().email())])
      .optional()
      .describe('CC recipient(s)'),
    bcc: z
      .union([z.string().email(), z.array(z.string().email())])
      .optional()
      .describe('BCC recipient(s)'),
    reply_to: z
      .union([z.string().email(), z.array(z.string().email())])
      .optional()
      .describe('Reply-to email address(es)'),
    tags: z
      .array(TagSchema)
      .max(50)
      .optional()
      .describe('Custom metadata tags for tracking (max 50)'),
  })
  .refine((data) => data.html || data.text, {
    message: 'Either html or text must be provided',
    path: ['html', 'text'],
  });

src/index.ts:52-56 (registration)

Tool registration in the MCP server: defines name, description, and inputSchema for listTools.

{
  name: 'resend_send_email',
  description:
    'Send a single email to one or more recipients. Supports HTML and plain text content, CC/BCC, reply-to, and custom tags for tracking.',
  inputSchema: zodToJsonSchema(SendEmailRequestSchema),

Resend MCP Server