set_focus · Mementos MCP: Risk & Policy

WHAT IT DOES

What set_focus does on Mementos

AI agents use set_focus 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 set_focus needs a policy

set_focus modifies an agent's active context or configuration setting (which project is in focus), which qualifies as Write since it creates or modifies data reversibly without deleting or executing external commands. The modification is reversible by setting a different focus.

From the tool's definition Tool description states it "Set focus for an agent on a project" and modifies which project "Memory ops will auto-scope to" — this changes agent state/configuration reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_focus Rate-limited

set_focus 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": {
    "set_focus": {
      "limits": [
        {
          "counter": "set_focus_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 set_focus

What does the set_focus tool do? +

Set focus for an agent on a project. Memory ops will auto-scope to that project. 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 set_focus? +

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

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

Can I rate-limit set_focus? +

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

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

set_focus 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.