update_reminder · Nexus Core MCP: Risk & Policy

WHAT IT DOES

What update_reminder does on Nexus Core

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

WHY IT NEEDS A POLICY

Why update_reminder needs a policy

The tool creates or modifies data (reminder records) in a reversible manner. Users can update reminder details like the body text, firing time, recurrence pattern, or status. While modifications are made, they can be undone by issuing another update_reminder call with different values. This fits the Write category.

From the tool's definition Tool description states 'Modify a reminder' with allowed change keys including body, fire_at, recurrence, and status. This is a reversible modification operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_reminder Rate-limited

update_reminder 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_reminder": {
      "limits": [
        {
          "counter": "update_reminder_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 Core, so you can run agents against it safely.

FAQ

Questions about update_reminder

What does the update_reminder tool do? +

Modify a reminder. Allowed change keys: body, fire_at (ISO), recurrence, status. It is categorised as a Write tool in the Nexus Core 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_reminder? +

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

What risk level is update_reminder? +

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

Can I rate-limit update_reminder? +

Yes. Add a rate_limit block to the update_reminder 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_reminder completely? +

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

update_reminder is provided by the Nexus Core MCP server (noumenon-ai/nexus-core). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.