Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:1103-1114 (registration)

  Registration of the 'get_forwarding_address' tool, including schema definition (forwardingEmail parameter) and handler function that calls the Gmail API to retrieve the specified forwarding address.
  server.tool("get_forwarding_address", "Gets the specified forwarding address", { forwardingEmail: z.string().describe("The forwarding address to be retrieved") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.forwardingAddresses.get({ userId: 'me', forwardingEmail: params.forwardingEmail }) return formatResponse(data) }) } )
• src/index.ts:1103-1114 (handler)

  The handler executes the tool logic by invoking Gmail's users.settings.forwardingAddresses.get API method with the provided forwardingEmail.
  server.tool("get_forwarding_address", "Gets the specified forwarding address", { forwardingEmail: z.string().describe("The forwarding address to be retrieved") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.forwardingAddresses.get({ userId: 'me', forwardingEmail: params.forwardingEmail }) return formatResponse(data) }) } )
• src/index.ts:1105-1107 (schema)

  Zod schema for input parameters: forwardingEmail (string, required).
  { forwardingEmail: z.string().describe("The forwarding address to be retrieved") },
• src/index.ts:50-80 (helper)

  Shared helper function handleTool that manages OAuth2 authentication, creates Gmail client, executes the provided API call, and handles errors uniformly across all tools.
  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}` }); } }