Gmail MCP

Instructions

Implementation Reference

• src/index.ts:929-940 (registration)

  Registration of the 'add_delegate' MCP tool, including description, Zod input schema, and inline async handler function that invokes the Gmail API to add a delegate.

  server.tool("add_delegate",
    "Adds a delegate to the specified account",
    {
      delegateEmail: z.string().describe("Email address of delegate to add")
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.delegates.create({ userId: 'me', requestBody: { delegateEmail: params.delegateEmail } })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:934-939 (handler)

  The core handler function for the add_delegate tool. It uses the shared handleTool helper to manage OAuth2 authentication, create a Gmail client, call the Gmail API to create a delegate, and format the response.

  async (params) => {
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.settings.delegates.create({ userId: 'me', requestBody: { delegateEmail: params.delegateEmail } })
      return formatResponse(data)
    })
  }

• src/index.ts:931-932 (schema)

  Input schema for add_delegate tool defined using Zod, requiring a delegateEmail string.

  {
    delegateEmail: z.string().describe("Email address of delegate to add")

• src/index.ts:49-65 (helper)

  Shared helper function handleTool used by add_delegate (and other tools) to handle OAuth2 client creation, credential validation, Gmail client instantiation, API call execution, and 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) {
      return `Tool execution failed: ${error.message}`
    }
  }

• src/index.ts:47-47 (helper)

  Helper function to format tool responses as MCP content blocks with JSON-stringified data.

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