Start authentication for a new account. Microsoft: returns device code URL. Google: returns OAuth URL. Both require auth_complete afterward. IMAP: completes immediately.
AI agents use auth_start to create or update resources in Mail Cal Drive — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mail Cal Drive environment.
This tool initiates an authentication flow that creates a new account session/credential. It's a Write operation as it creates new auth state, though it doesn't complete on its own for Microsoft/Google. It's not purely Read since it initiates a side-effecting process. Severity is medium because unauthorized account linking could allow an attacker to connect malicious accounts to the server.
From the tool's definition Start authentication for a new account... requires auth_complete afterward
Attacks that exploit this kind of access
Start authentication for a new account. Microsoft: returns device code URL. Google: returns OAuth URL. Both require auth_complete afterward. IMAP: completes immediately. It is categorised as a Write tool in the Mail Cal Drive MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mail Cal Drive MCP server in PolicyLayer and add a rule for auth_start: 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 Mail Cal Drive. Nothing to install.
auth_start 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 auth_start 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 auth_start. 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.
auth_start is provided by the Mail Cal Drive MCP server (rumbitopi/mail-cal-drive-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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