Gmail MCP

Instructions

Implementation Reference

• src/index.ts:571-589 (handler)

  The handler function for the 'list_messages' tool. It invokes the Gmail API's users.messages.list method with user-provided parameters, processes each message's payload by decoding bodies and filtering headers if applicable, and returns a formatted JSON response.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.messages.list({ userId: 'me', ...params }) if (data.messages) { data.messages = data.messages.map((message: Message) => { if (message.payload) { message.payload = processMessagePart( message.payload, params.includeBodyHtml ) } return message }) } return formatResponse(data) }) }
• src/index.ts:563-570 (schema)

  The Zod input schema for the 'list_messages' tool, defining optional parameters for pagination, querying, filtering by labels, including spam/trash, and body processing options.
  { maxResults: z.number().optional().describe("Maximum number of messages to return. Accepts values between 1-500"), pageToken: z.string().optional().describe("Page token to retrieve a specific page of results"), q: z.string().optional().describe("Only return messages matching the specified query. Supports the same query format as the Gmail search box"), labelIds: z.array(z.string()).optional().describe("Only return messages with labels that match all of the specified label IDs"), includeSpamTrash: z.boolean().optional().describe("Include messages 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:561-590 (registration)

  The registration of the 'list_messages' tool on the MCP server using server.tool(), specifying name, description, schema, and handler.
  server.tool("list_messages", "List messages in the user's mailbox with optional filtering", { maxResults: z.number().optional().describe("Maximum number of messages to return. Accepts values between 1-500"), pageToken: z.string().optional().describe("Page token to retrieve a specific page of results"), q: z.string().optional().describe("Only return messages matching the specified query. Supports the same query format as the Gmail search box"), labelIds: z.array(z.string()).optional().describe("Only return messages with labels that match all of the specified label IDs"), includeSpamTrash: z.boolean().optional().describe("Include messages 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.messages.list({ userId: 'me', ...params }) if (data.messages) { data.messages = data.messages.map((message: Message) => { if (message.payload) { message.payload = processMessagePart( message.payload, params.includeBodyHtml ) } return message }) } return formatResponse(data) }) } )
• src/index.ts:79-93 (helper)

  Helper function used in the handler to recursively process message parts: decodes base64 data to UTF-8 for text bodies (plain and optionally HTML), recurses on multipart, and filters headers to a predefined list.
  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 }
• src/index.ts:49-65 (helper)

  Shared helper function used by the handler (and other tools) to manage OAuth2 authentication, validate credentials, create Gmail client, execute the API call, and handle 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}` } }