Gmail's MCP Server Will Reject Any OAuth Client Not Marked Agentic
From Nov. 11 Google Workspace MCP servers will turn away OAuth clients not marked as AI agents. Apps that mix agent and REST features need two clients.
Starting Nov. 11, Google Workspace MCP servers, Gmail’s included, will reject requests from any OAuth client that is not marked as an AI agent, Google said in its Oct. 12 Gmail API release notes. The mark is a checkbox, “Use this client for an AI-powered agent,” in the Clients page of Google Auth Platform.
Unmarked Clients Stay Locked Out
Clients not marked as agentic by Nov. 12 stay non-agentic and cannot call the MCP servers, Google said. The only way back in is a new OAuth client marked as agentic, plus an app update to use it.
Apps that only call the Gmail REST API are not affected, according to the notes. An app that does both gets a split. Google said to create a separate OAuth client for the agent features, mark only that one as agentic and keep the old client for everything else.
The Gmail MCP Server Reads Mail and Drafts Replies
The Gmail MCP server is in Google’s Workspace Developer Preview Program, according to Google’s setup guide. It lives at https://gmailmcp.googleapis.com/mcp/v1 and needs the Gmail API and the Gmail MCP API enabled in a Google Cloud project. Google’s reference page lists 10 tools: search_threads, get_thread, get_message, list_labels, list_drafts, create_draft and four that add or remove labels on a message or thread.
The guide says the server reads data and takes action. Action means creating drafts and labeling messages. It names Google Antigravity and Claude as example hosts. The server inherits the signed-in user’s permissions and data governance controls, the guide said.
Other Workspace Servers Follow the Same Rule
The Nov. 11 cutoff covers every Google Workspace MCP server, Google said. Its general setup guide lists servers for Gmail, Drive, Docs, Sheets, Slides, Calendar, Chat, People and Classroom. Each is enabled as its own service.
The take
We think Google is separating AI agents from ordinary apps. A client marked agentic is a label Google can see. That gives it a way to apply different limits or reviews to agents later without touching ordinary apps. The label costs a checkbox today. Set it early.
The practical risk is a team that finds out on Nov. 12. A client that runs both a sync job and an agent feature cannot be fixed by ticking the box. The box applies to everything that client does. Google tells teams to split the client.
Teams should list every OAuth client that reaches Gmail and ask which ones talk to an MCP host. Create a new agentic client for those, move the agent code over, and leave the REST sync on the old client. Finish before Nov. 11.
