Gmail MCP

Instructions

Implementation Reference

• src/index.ts:1083-1092 (handler)

  Registration and inline handler for the 'list_forwarding_addresses' tool. It calls the Gmail API to list forwarding addresses via handleTool and formatResponse, with empty input schema.

  server.tool("list_forwarding_addresses",
    "Lists the forwarding addresses for the specified account",
    {},
    async () => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.forwardingAddresses.list({ userId: 'me' })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:49-65 (helper)

  Shared helper function handleTool used by all tools, including list_forwarding_addresses, to handle OAuth2 authentication, Gmail client creation, and API call execution.

  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) {
      return `Tool execution failed: ${error.message}`
    }
  }

• src/index.ts:47-47 (helper)

  Helper function to format tool responses as MCP content blocks.

  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })