update_agent · Mementos MCP: Risk & Policy

WHAT IT DOES

What update_agent does on Mementos

AI agents use update_agent 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 update_agent needs a policy

This tool creates or modifies data reversibly by updating agent metadata and properties. Changes to agent configuration (name, description, role, metadata, active_project_id) can be reversed through subsequent updates, making it Write rather than Destructive.

From the tool's definition Tool name 'update_agent' and description 'Update agent name, description, role, metadata, or active_project_id' explicitly perform modifications to agent configuration data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_agent Rate-limited

update_agent 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": {
    "update_agent": {
      "limits": [
        {
          "counter": "update_agent_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 update_agent

What does the update_agent tool do? +

Update agent name, description, role, metadata, or active_project_id. 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 update_agent? +

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

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

Can I rate-limit update_agent? +

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

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

update_agent 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.