Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:1220-1231 (registration)

  Registration of the 'verify_send_as' tool including description, input schema (sendAsEmail: string), and inline handler that uses handleTool for authentication and calls Gmail API gmail.users.settings.sendAs.verify to send a verification email to the alias.
  server.tool("verify_send_as", "Sends a verification email to the specified send-as alias", { sendAsEmail: z.string().describe("The send-as alias to be verified") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.sendAs.verify({ userId: 'me', sendAsEmail: params.sendAsEmail }) return formatResponse(data) }) } )
• src/index.ts:1225-1231 (handler)

  The handler function executes the tool logic: wraps the Gmail API call to verify/send email to sendAsEmail using handleTool for OAuth2 handling and error management, formats response.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.sendAs.verify({ userId: 'me', sendAsEmail: params.sendAsEmail }) return formatResponse(data) }) } )
• src/index.ts:1222-1224 (schema)

  Input schema for verify_send_as tool: requires sendAsEmail as string.
  { sendAsEmail: z.string().describe("The send-as alias to be verified") },
• src/index.ts:50-80 (helper)

  Shared helper function handleTool used by verify_send_as (and other tools) for OAuth2 client creation, credential validation, Gmail client instantiation, API call execution, and authentication error handling.
  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}` }); } }