invalidate_fact · Memoraeu MCP: Risk & Policy

WHAT IT DOES

What invalidate_fact does on Memoraeu

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

WHY IT NEEDS A POLICY

Why invalidate_fact needs a policy

Invalidating/expiring a fact modifies its state (marks it as expired) rather than permanently deleting it, making it a reversible write operation. It changes the fact's status but doesn't purge it from storage. Misuse could cause loss of access to important stored facts, hence medium severity.

From the tool's definition Mark a fact as expired by its ID

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

invalidate_fact Rate-limited

invalidate_fact 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": {
    "invalidate_fact": {
      "limits": [
        {
          "counter": "invalidate_fact_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 Memoraeu, so you can run agents against it safely.

FAQ

Questions about invalidate_fact

What does the invalidate_fact tool do? +

Mark a fact as expired by its ID. It is categorised as a Write tool in the Memoraeu MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on invalidate_fact? +

Register the Memoraeu MCP server in PolicyLayer and add a rule for invalidate_fact: 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 Memoraeu. Nothing to install.

What risk level is invalidate_fact? +

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

Can I rate-limit invalidate_fact? +

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

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

invalidate_fact is provided by the Memoraeu MCP server (pquattro/memoraeu-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.