Connect a new Google account or re-authenticate an existing one. If sign-in was recently completed in the browser, this will verify the connection without opening a new browser window.
AI agents use add_account to create or update resources in Google Calendar MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Google Calendar MCP environment.
The tool creates or modifies authentication credentials and account associations, which is reversible (accounts can be disconnected/removed). This is a Write operation rather than Read (it changes state), but not Destructive (accounts are not permanently deleted) or Execute (not running arbitrary code).
From the tool's definition Tool description states it 'Connect[s] a new Google account or re-authenticate[s] an existing one', which involves modifying the authentication state and account configuration of the system.
Attacks that exploit this kind of access
Connect a new Google account or re-authenticate an existing one. If sign-in was recently completed in the browser, this will verify the connection without opening a new browser window. It is categorised as a Write tool in the Google Calendar MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Google Calendar MCP server in PolicyLayer and add a rule for add_account: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Google Calendar MCP. Nothing to install.
add_account is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add_account rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for add_account. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
add_account is provided by the Google Calendar MCP server (paytience/google-calendar-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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