renew_file_reservations · MCP Agent Mail MCP: Risk & Policy

WHAT IT DOES

What renew_file_reservations does on MCP Agent Mail

AI agents use renew_file_reservations to create or update resources in MCP Agent Mail — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP Agent Mail environment.

WHY IT NEEDS A POLICY

Why renew_file_reservations needs a policy

Based on the server context about 'file reservation leases to prevent agents from overwriting each other's work,' renewing file reservations likely extends or updates existing lease records — a Write operation. However, the empty description lowers confidence. Severity is medium because misuse could block other agents from accessing files in a multi-agent environment, but it does not directly destroy data.

From the tool's definition Tool name: renew_file_reservations; description is empty

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

renew_file_reservations Rate-limited

renew_file_reservations stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "renew_file_reservations": {
      "limits": [
        {
          "counter": "renew_file_reservations_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP Agent Mail, so you can run agents against it safely.

FAQ

Questions about renew_file_reservations

What does the renew_file_reservations tool do? +

renew_file_reservations. It is categorised as a Write tool in the MCP Agent Mail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on renew_file_reservations? +

Register the MCP Agent Mail MCP server in PolicyLayer and add a rule for renew_file_reservations: 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 MCP Agent Mail. Nothing to install.

What risk level is renew_file_reservations? +

renew_file_reservations is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit renew_file_reservations? +

Yes. Add a rate_limit block to the renew_file_reservations 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.

How do I block renew_file_reservations completely? +

Set action: deny in the PolicyLayer policy for renew_file_reservations. 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.

What MCP server provides renew_file_reservations? +

renew_file_reservations is provided by the MCP Agent Mail MCP server (omelchmichael/mcp_agent_mail). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.