Gmail MCP

Instructions

Implementation Reference

• src/index.ts:820-829 (registration)

  Registration of the 'get_language' MCP tool. It has no input parameters (empty schema), and the handler fetches the user's Gmail language settings using the Gmail API and formats the response using shared helpers.

  server.tool("get_language",
    "Gets language settings",
    {},
    async () => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.getLanguage({ userId: 'me' })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:823-828 (handler)

  The inline handler function for the 'get_language' tool. It uses the shared 'handleTool' helper to execute the Gmail API call to retrieve language settings.

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

• src/index.ts:49-65 (helper)

  Shared helper function 'handleTool' used by 'get_language' and other tools to manage OAuth2 authentication, create Gmail client, execute the API call, and handle errors.

  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)

  Shared helper function 'formatResponse' used by 'get_language' and other tools to format API responses into MCP content format.

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