Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:1201-1218 (registration)

  Registers the 'update_send_as' MCP tool, providing description, input schema validation, and the handler function.
  server.tool("update_send_as", "Updates a send-as alias", { sendAsEmail: z.string().describe("The send-as alias to be updated"), displayName: z.string().optional().describe("A name that appears in the 'From:' header"), replyToAddress: z.string().optional().describe("An optional email address that is included in a 'Reply-To:' header"), signature: z.string().optional().describe("An optional HTML signature"), isPrimary: z.boolean().optional().describe("Whether this address is the primary address"), treatAsAlias: z.boolean().optional().describe("Whether Gmail should treat this address as an alias") }, async (params) => { const { sendAsEmail, ...updateData } = params return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.sendAs.update({ userId: 'me', sendAsEmail, requestBody: updateData }) return formatResponse(data) }) } )
• src/index.ts:1211-1217 (handler)

  Executes the tool logic: destructures params to separate sendAsEmail from update data, uses shared handleTool to authenticate and call Gmail API's users.settings.sendAs.update method, then formats the response.
  async (params) => { const { sendAsEmail, ...updateData } = params return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.sendAs.update({ userId: 'me', sendAsEmail, requestBody: updateData }) return formatResponse(data) }) }
• src/index.ts:1203-1210 (schema)

  Zod schema defining input parameters for the tool, including required sendAsEmail and optional fields for updating the send-as alias configuration.
  { sendAsEmail: z.string().describe("The send-as alias to be updated"), displayName: z.string().optional().describe("A name that appears in the 'From:' header"), replyToAddress: z.string().optional().describe("An optional email address that is included in a 'Reply-To:' header"), signature: z.string().optional().describe("An optional HTML signature"), isPrimary: z.boolean().optional().describe("Whether this address is the primary address"), treatAsAlias: z.boolean().optional().describe("Whether Gmail should treat this address as an alias") },
• src/index.ts:50-80 (helper)

  Shared utility function used by all Gmail tools to handle OAuth2 authentication, credential validation, Gmail client creation, API call execution, and error handling with specific auth error responses.
  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}` }); } }