retain · Engram MCP: Risk & Policy

WHAT IT DOES

What retain does on Engram

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

WHY IT NEEDS A POLICY

Why retain needs a policy

The tool creates and stores new data (facts, entities, relationships) in a memory system. This is a reversible write operation — data is added but not irreversibly destroyed. Misuse could lead to polluting the memory store with false or malicious facts, which could influence future recalls or reflections, hence medium severity.

From the tool's definition "Store new information in memory. Extracts facts, entities, and relationships from text."

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

retain Rate-limited

retain 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": {
    "retain": {
      "limits": [
        {
          "counter": "retain_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 Engram, so you can run agents against it safely.

FAQ

Questions about retain

What does the retain tool do? +

Store new information in memory. Extracts facts, entities, and relationships from text. It is categorised as a Write tool in the Engram MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on retain? +

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

What risk level is retain? +

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

Can I rate-limit retain? +

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

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

retain is provided by the Engram MCP server (reallyartificial/engram). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.