memory_rate · Mementos MCP: Risk & Policy

WHAT IT DOES

What memory_rate does on Mementos

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

WHY IT NEEDS A POLICY

Why memory_rate needs a policy

This tool modifies metadata associated with a memory entry (its usefulness rating), which is a reversible write operation. It does not delete data, execute code, or involve financial transactions. The blast radius is low since misuse would only affect quality/ranking signals, not core data integrity.

From the tool's definition "Rate a memory as useful or not useful. Provides feedback for memory quality tracking."

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

memory_rate Rate-limited

memory_rate 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": {
    "memory_rate": {
      "limits": [
        {
          "counter": "memory_rate_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 Mementos, so you can run agents against it safely.

FAQ

Questions about memory_rate

What does the memory_rate tool do? +

Rate a memory as useful or not useful. Provides feedback for memory quality tracking. It is categorised as a Write tool in the Mementos MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on memory_rate? +

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

What risk level is memory_rate? +

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

Can I rate-limit memory_rate? +

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

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

memory_rate is provided by the Mementos MCP server (@hasna/mementos). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.