expire_event · Fastly NGWAF MCP Server MCP: Risk & Policy

WHAT IT DOES

What expire_event does on Fastly NGWAF MCP Server

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

WHY IT NEEDS A POLICY

Why expire_event needs a policy

The tool reverses a firewall blocking action by expiring/unblocking an IP address. This is a Write operation because it modifies firewall state (changes an IP from blocked to unblocked), not Destructive because the original event/block record can theoretically be re-created or the IP can be re-blocked.

From the tool's definition Tool performs 'Manually expire an event (unblock IP)' — this modifies the state of a firewall event/block by removing it, which is a reversible state change.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

expire_event Rate-limited

expire_event 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": {
    "expire_event": {
      "limits": [
        {
          "counter": "expire_event_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about expire_event

What does the expire_event tool do? +

Manually expire an event (unblock IP). It is categorised as a Write tool in the Fastly NGWAF MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on expire_event? +

Register the Fastly NGWAF MCP Server MCP server in PolicyLayer and add a rule for expire_event: 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 Fastly NGWAF MCP Server. Nothing to install.

What risk level is expire_event? +

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

Can I rate-limit expire_event? +

Yes. Add a rate_limit block to the expire_event 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 expire_event completely? +

Set action: deny in the PolicyLayer policy for expire_event. 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 expire_event? +

expire_event is provided by the Fastly NGWAF MCP Server MCP server (purpleax/fastlymcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.