update · Nexus Memory MCP: Risk & Policy

WHAT IT DOES

What update does on Nexus Memory

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

WHY IT NEEDS A POLICY

Why update needs a policy

This tool creates or modifies data within the persistent memory store. While 'update' is reversible (a user could update again or use 'forget' to remove), it directly alters stored information that other agents may depend on. The 'anti-poisoning features' mentioned in the server description suggest the system recognizes risks from malicious memory updates.

From the tool's definition 'Update an existing memory in-place without losing metadata' — modifies stored data reversibly. The tool changes memory content while preserving metadata, a classic write operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update Rate-limited

update 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": {
      "limits": [
        {
          "counter": "update_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 Nexus Memory, so you can run agents against it safely.

FAQ

Questions about update

What does the update tool do? +

Update an existing memory in-place without losing metadata. It is categorised as a Write tool in the Nexus Memory 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? +

Register the Nexus Memory MCP server in PolicyLayer and add a rule for update: 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 Nexus Memory. Nothing to install.

What risk level is update? +

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

Can I rate-limit update? +

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

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

update is provided by the Nexus Memory MCP server (neboy72/nexus-memory). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.