Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:838-847 (registration)

  Registration of the 'get_language' MCP tool. It defines an empty input schema and an inline handler that uses the shared 'handleTool' helper to authenticate and call the Gmail API's users.settings.getLanguage method to retrieve the user's language settings, then formats the response.
  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:838-847 (handler)

  The inline handler function for the 'get_language' tool executes the core logic: invokes Gmail API to get language settings after authentication via handleTool.
  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:50-66 (helper)

  Shared helper function 'handleTool' used by 'get_language' (and other tools) to handle OAuth2 client creation, credential validation, Gmail client instantiation, and execution of the API call provided as callback.
  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:48-48 (helper)

  Helper function 'formatResponse' used to format the Gmail API response into MCP-compatible content structure (text with JSON string).
  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })