Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:311-331 (registration)

  Registration of the 'get_draft' tool using McpServer.tool(), including description, input schema, and inline handler function.
  server.tool("get_draft", "Get a specific draft by ID", { id: z.string().describe("The ID of the draft 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.drafts.get({ userId: 'me', id: params.id, format: 'full' }) if (data.message?.payload) { data.message.payload = processMessagePart( data.message.payload, params.includeBodyHtml ) } return formatResponse(data) }) } )
• src/index.ts:317-330 (handler)

  The core handler logic for 'get_draft': fetches the draft via Gmail API, optionally decodes and processes the message payload (filtering headers, decoding base64 bodies), and formats the JSON response.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.drafts.get({ userId: 'me', id: params.id, format: 'full' }) if (data.message?.payload) { data.message.payload = processMessagePart( data.message.payload, params.includeBodyHtml ) } return formatResponse(data) }) }
• src/index.ts:313-316 (schema)

  Zod schema defining input parameters for the 'get_draft' tool: required 'id' (draft ID) and optional 'includeBodyHtml' flag.
  { id: z.string().describe("The ID of the draft 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:50-80 (helper)

  Shared helper function used by get_draft (and other tools) to handle OAuth2 authentication, client creation, API execution, and error handling (especially auth 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) { // Check for specific authentication errors if ( error.message?.includes("invalid_grant") || error.message?.includes("refresh_token") || error.message?.includes("invalid_client") || error.message?.includes("unauthorized_client") || error.code === 401 || error.code === 403 ) { return formatResponse({ error: `Authentication failed: ${error.message}. Please re-authenticate by running: npx @shinzolabs/gmail-mcp auth`, }); } return formatResponse({ error: `Tool execution failed: ${error.message}` }); } }
• src/index.ts:94-108 (helper)

  Recursive helper to process message parts in drafts/messages: decodes base64 bodies (unless HTML and not requested), recurses into parts, filters headers to common ones.
  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 }