entity_link · Mementos MCP: Risk & Policy

WHAT IT DOES

What entity_link does on Mementos

AI agents use entity_link 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 entity_link needs a policy

This tool creates a relationship/association between an entity and a memory, which is a reversible write operation. It modifies the data model by adding a link but does not delete or overwrite existing data, nor does it execute code or involve financial transactions.

From the tool's definition Link an entity to a memory with a role (subject, object, or context)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

entity_link Rate-limited

entity_link 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": {
    "entity_link": {
      "limits": [
        {
          "counter": "entity_link_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 entity_link

What does the entity_link tool do? +

Link an entity to a memory with a role (subject, object, or context). 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 entity_link? +

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

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

Can I rate-limit entity_link? +

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

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

entity_link 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.