set_memento_decay_factor · MCP Memento MCP: Risk & Policy

WHAT IT DOES

What set_memento_decay_factor does on MCP Memento

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

WHY IT NEEDS A POLICY

Why set_memento_decay_factor needs a policy

The tool modifies memento system parameters (decay factor) which affects how confidence scores degrade over time. This is a Write operation—it changes system state reversibly. Severity is medium because misconfiguration could degrade the quality of recalled information for the AI agent, but the change can be reverted.

From the tool's definition Tool name 'set_memento_decay_factor' combined with server context showing 'intelligent confidence tracking' and sibling tool 'apply_memento_confidence_decay' indicates this tool modifies decay parameters affecting stored mementos.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_memento_decay_factor Rate-limited

set_memento_decay_factor 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_memento_decay_factor": {
      "limits": [
        {
          "counter": "set_memento_decay_factor_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 MCP Memento, so you can run agents against it safely.

FAQ

Questions about set_memento_decay_factor

What does the set_memento_decay_factor tool do? +

set_memento_decay_factor. It is categorised as a Write tool in the MCP Memento 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_memento_decay_factor? +

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

What risk level is set_memento_decay_factor? +

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

Can I rate-limit set_memento_decay_factor? +

Yes. Add a rate_limit block to the set_memento_decay_factor 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_memento_decay_factor completely? +

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

set_memento_decay_factor is provided by the MCP Memento MCP server (x-hannibal/mcp-memento). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.