entity_create · Mementos MCP: Risk & Policy

WHAT IT DOES

What entity_create does on Mementos

AI agents use entity_create 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_create needs a policy

This tool creates new data structures (entities) in a knowledge graph system, which is a reversible modification operation. It does not execute arbitrary code, delete data irreversibly, move money, or retrieve existing data. Creation of structured data in a memory/knowledge system is classified as Write.

From the tool's definition Tool name 'entity_create' explicitly performs a create operation, creating knowledge graph entities. The description confirms it 'Create a knowledge graph entity' with various types (person, project, tool, concept, file, api, pattern, organization).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

entity_create Rate-limited

entity_create 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_create": {
      "limits": [
        {
          "counter": "entity_create_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_create

What does the entity_create tool do? +

Create a knowledge graph entity (person, project, tool, concept, file, api, pattern, organization). 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_create? +

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

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

Can I rate-limit entity_create? +

Yes. Add a rate_limit block to the entity_create 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_create completely? +

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

entity_create 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.