memory_acl_set · Mementos MCP: Risk & Policy

WHAT IT DOES

What memory_acl_set does on Mementos

AI agents use memory_acl_set 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_acl_set needs a policy

This tool modifies access control rules, which is a reversible configuration change. While it affects security permissions (raising severity above 'low'), it does not delete data, execute code, or move money. Write is appropriate because ACL changes can be updated or reverted.

From the tool's definition Tool name 'memory_acl_set' and description 'Set an access control rule for an agent' indicate the tool creates or modifies access control configuration. The verb 'Set' is explicitly modification-oriented.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

memory_acl_set Rate-limited

memory_acl_set 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_acl_set": {
      "limits": [
        {
          "counter": "memory_acl_set_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_acl_set

What does the memory_acl_set tool do? +

Set an access control rule for an agent. Patterns use * for glob matching (e.g.,. 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_acl_set? +

Register the Mementos MCP server in PolicyLayer and add a rule for memory_acl_set: 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_acl_set? +

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

Can I rate-limit memory_acl_set? +

Yes. Add a rate_limit block to the memory_acl_set 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_acl_set completely? +

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

memory_acl_set 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.