Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:739-773 (registration)

  Registers the 'list_threads' MCP tool with description, input schema using Zod, and inline handler function that calls Gmail API to list threads.
  server.tool("list_threads", "List threads in the user's mailbox", { maxResults: z.number().optional().describe("Maximum number of threads to return"), pageToken: z.string().optional().describe("Page token to retrieve a specific page of results"), q: z.string().optional().describe("Only return threads matching the specified query"), labelIds: z.array(z.string()).optional().describe("Only return threads with labels that match all of the specified label IDs"), includeSpamTrash: z.boolean().optional().describe("Include threads from SPAM and TRASH in the results"), includeBodyHtml: z.boolean().optional().describe("Whether to include the parsed HTML in the return for each body, excluded by default because they can be excessively large"), }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.threads.list({ userId: 'me', ...params }) if (data.threads) { data.threads = data.threads.map(thread => { if (thread.messages) { thread.messages = thread.messages.map(message => { if (message.payload) { message.payload = processMessagePart( message.payload, params.includeBodyHtml ) } return message }) } return thread }) } return formatResponse(data) }) } )
• src/index.ts:749-772 (handler)

  The handler function for 'list_threads' tool. It invokes handleTool which authenticates, calls gmail.users.threads.list with params, optionally decodes and processes message payloads using processMessagePart, and returns formatted JSON response.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.threads.list({ userId: 'me', ...params }) if (data.threads) { data.threads = data.threads.map(thread => { if (thread.messages) { thread.messages = thread.messages.map(message => { if (message.payload) { message.payload = processMessagePart( message.payload, params.includeBodyHtml ) } return message }) } return thread }) } return formatResponse(data) }) }
• src/index.ts:742-748 (schema)

  Zod input schema for 'list_threads' tool parameters, validating optional filters like maxResults, query (q), labels, etc.
  maxResults: z.number().optional().describe("Maximum number of threads to return"), pageToken: z.string().optional().describe("Page token to retrieve a specific page of results"), q: z.string().optional().describe("Only return threads matching the specified query"), labelIds: z.array(z.string()).optional().describe("Only return threads with labels that match all of the specified label IDs"), includeSpamTrash: z.boolean().optional().describe("Include threads from SPAM and TRASH in the results"), includeBodyHtml: z.boolean().optional().describe("Whether to include the parsed HTML in the return for each body, excluded by default because they can be excessively large"), },
• src/index.ts:50-66 (helper)

  Shared helper function used by 'list_threads' (and other tools) to handle OAuth2 authentication, create Gmail client, execute the API call, and catch errors.
  const handleTool = async (queryConfig: Record<string, any> | undefined, apiCall: (gmail: gmail_v1.Gmail) => Promise<any>) => { try { const oauth2Client = queryConfig ? createOAuth2Client(queryConfig) : defaultOAuth2Client if (!oauth2Client) throw new Error('OAuth2 client could not be created, please check your credentials') const credentialsAreValid = await validateCredentials(oauth2Client) if (!credentialsAreValid) throw new Error('OAuth2 credentials are invalid, please re-authenticate') const gmailClient = queryConfig ? google.gmail({ version: 'v1', auth: oauth2Client }) : defaultGmailClient if (!gmailClient) throw new Error('Gmail client could not be created, please check your credentials') const result = await apiCall(gmailClient) return result } catch (error: any) { return `Tool execution failed: ${error.message}` } }
• src/index.ts:80-94 (helper)

  Helper to recursively decode base64 bodies (except HTML unless specified), filter headers, used in 'list_threads' to process thread message payloads.
  const processMessagePart = (messagePart: MessagePart, includeBodyHtml = false): MessagePart => { if ((messagePart.mimeType !== 'text/html' || includeBodyHtml) && messagePart.body) { messagePart.body = decodedBody(messagePart.body) } if (messagePart.parts) { messagePart.parts = messagePart.parts.map(part => processMessagePart(part, includeBodyHtml)) } if (messagePart.headers) { messagePart.headers = messagePart.headers.filter(header => RESPONSE_HEADERS_LIST.includes(header.name || '')) } return messagePart }