Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:341-368 (handler)

  Handler function for the 'list_drafts' tool. Lists Gmail drafts using the Gmail API, handles pagination by fetching all pages until no nextPageToken, processes each draft's message payload (decoding bodies if applicable, filtering headers), and returns a formatted JSON response.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { let drafts: Draft[] = [] const { data } = await gmail.users.drafts.list({ userId: 'me', ...params }) drafts.push(...data.drafts || []) while (data.nextPageToken) { const { data: nextData } = await gmail.users.drafts.list({ userId: 'me', ...params, pageToken: data.nextPageToken }) drafts.push(...nextData.drafts || []) } if (drafts) { drafts = drafts.map(draft => { if (draft.message?.payload) { draft.message.payload = processMessagePart( draft.message.payload, params.includeBodyHtml ) } return draft }) } return formatResponse(drafts) }) }
• src/index.ts:335-340 (schema)

  Zod input schema defining parameters for the list_drafts tool: maxResults, q (search query), includeSpamTrash, includeBodyHtml.
  { maxResults: z.number().optional().describe("Maximum number of drafts to return. Accepts values between 1-500"), q: z.string().optional().describe("Only return drafts matching the specified query. Supports the same query format as the Gmail search box"), includeSpamTrash: z.boolean().optional().describe("Include drafts 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:333-368 (registration)

  Registration of the 'list_drafts' tool on the McpServer instance, including name, description, input schema, and handler function.
  server.tool("list_drafts", "List drafts in the user's mailbox", { maxResults: z.number().optional().describe("Maximum number of drafts to return. Accepts values between 1-500"), q: z.string().optional().describe("Only return drafts matching the specified query. Supports the same query format as the Gmail search box"), includeSpamTrash: z.boolean().optional().describe("Include drafts 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) => { let drafts: Draft[] = [] const { data } = await gmail.users.drafts.list({ userId: 'me', ...params }) drafts.push(...data.drafts || []) while (data.nextPageToken) { const { data: nextData } = await gmail.users.drafts.list({ userId: 'me', ...params, pageToken: data.nextPageToken }) drafts.push(...nextData.drafts || []) } if (drafts) { drafts = drafts.map(draft => { if (draft.message?.payload) { draft.message.payload = processMessagePart( draft.message.payload, params.includeBodyHtml ) } return draft }) } return formatResponse(drafts) }) }
• src/index.ts:50-80 (helper)

  Shared helper function used by list_drafts (and other tools) to handle OAuth2 client creation/validation, Gmail client setup, API call 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)

  Helper function to process message parts: decodes base64 bodies (text/plain or text/html if flagged), recursively processes parts, filters headers to common response headers.
  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 }