Gmail MCP Server

import {z} from 'zod'; import type {McpServer} from '@modelcontextprotocol/sdk/server/mcp.js'; import type {Config} from './types.js'; import {makeGmailApiCall} from '../utils/gmail-api.js'; import {jsonResult} from '../utils/response.js'; const inputSchema = { to: z.string().describe('Recipient email address(es), comma-separated for multiple'), subject: z.string().describe('Email subject'), body: z.string().describe('Email body (plain text)'), cc: z.string().optional().describe('CC recipients, comma-separated'), bcc: z.string().optional().describe('BCC recipients, comma-separated'), threadId: z.string().optional().describe('Thread ID to reply to'), inReplyTo: z.string().optional().describe('Message-ID header of the message being replied to'), }; const outputSchema = z.object({ id: z.string(), threadId: z.string(), labelIds: z.array(z.string()).optional(), }); /** * Create an RFC 2822 formatted email message and base64url encode it. */ function createRawMessage(options: { to: string; subject: string; body: string; cc?: string; bcc?: string; inReplyTo?: string; }): string { const lines: string[] = []; lines.push(`To: ${options.to}`); if (options.cc) { lines.push(`Cc: ${options.cc}`); } if (options.bcc) { lines.push(`Bcc: ${options.bcc}`); } lines.push(`Subject: ${options.subject}`); if (options.inReplyTo) { lines.push(`In-Reply-To: ${options.inReplyTo}`); lines.push(`References: ${options.inReplyTo}`); } lines.push('Content-Type: text/plain; charset=utf-8'); lines.push(''); lines.push(options.body); const message = lines.join('\r\n'); // Base64url encode (replace + with -, / with _, remove =) return Buffer.from(message) .toString('base64') .replace(/\+/g, '-') .replace(/\//g, '_') .replace(/=+$/, ''); } export function registerMessageSend(server: McpServer, config: Config): void { server.registerTool( 'message_send', { title: 'Send message', description: 'Send an email message. Can also be used to reply to existing threads.', inputSchema, outputSchema, }, async ({to, subject, body, cc, bcc, threadId, inReplyTo}) => { const raw = createRawMessage({ to, subject, body, ...(cc && {cc}), ...(bcc && {bcc}), ...(inReplyTo && {inReplyTo}), }); const requestBody: {raw: string; threadId?: string} = {raw}; if (threadId) { requestBody.threadId = threadId; } const result = await makeGmailApiCall('POST', '/users/me/messages/send', config.token, requestBody); return jsonResult(outputSchema.parse(result)); }, ); }