update_language

Instructions

Implementation Reference

• src/index.ts:921-926 (handler)

  Handler function for the 'update_language' tool. It invokes the Gmail API's users.settings.updateLanguage method via the shared handleTool wrapper to update the display language.

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

• src/index.ts:918-920 (schema)

  Input schema using Zod for validating the 'displayLanguage' parameter of the update_language tool.

  {
    displayLanguage: z.string().describe("The language to display Gmail in, formatted as an RFC 3066 Language Tag")
  },

• src/index.ts:916-927 (registration)

  Registration of the 'update_language' tool on the MCP server, including name, description, schema, and handler.

  server.tool("update_language",
    "Updates language settings",
    {
      displayLanguage: z.string().describe("The language to display Gmail in, formatted as an RFC 3066 Language Tag")
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.updateLanguage({ userId: 'me', requestBody: params })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:50-80 (helper)

  Shared helper function used by all Gmail tools, including update_language, to handle OAuth2 authentication, client creation, error handling, 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) {
      // 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}` });
    }
  }