Gmail MCP

Instructions

Implementation Reference

• src/index.ts:548-557 (handler)

  Inline handler function for the 'get_message' MCP tool. It invokes the shared handleTool utility with an API callback that fetches the full Gmail message by ID, processes its payload (decoding bodies, filtering headers), and returns a formatted text/JSON response.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.messages.get({ userId: 'me', id: params.id, format: 'full' }) if (data.payload) { data.payload = processMessagePart(data.payload, params.includeBodyHtml) } return formatResponse(data) })
• src/index.ts:544-547 (schema)

  Input schema for 'get_message' tool using Zod: requires 'id' string (message ID), optional 'includeBodyHtml' boolean to control HTML body inclusion in response.
  { id: z.string().describe("The ID of the message to retrieve"), 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:542-559 (registration)

  Registration of the 'get_message' tool on the McpServer instance, specifying name, description, input schema, and handler function.
  server.tool("get_message", "Get a specific message by ID with format options", { id: z.string().describe("The ID of the message to retrieve"), 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.get({ userId: 'me', id: params.id, format: 'full' }) if (data.payload) { data.payload = processMessagePart(data.payload, params.includeBodyHtml) } return formatResponse(data) }) } )
• src/index.ts:49-65 (helper)

  Core helper function used by 'get_message' (and all tools): handles OAuth2 client creation/validation, Gmail client setup, executes the provided Gmail API callback, catches 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:79-93 (helper)

  Recursive helper to process Gmail message parts for 'get_message': decodes base64 bodies for text/* (html if flagged), recurses into parts, retains only key headers (Date, From, To, Subject, etc.).
  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 }