add_to_group · Nexus Core MCP: Risk & Policy

WHAT IT DOES

What add_to_group does on Nexus Core

AI agents use add_to_group 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 add_to_group needs a policy

This tool modifies contact/group data by adding a contact to a group or creating a new group. These are write operations—data is created or updated, but the changes are reversible (contacts can be removed from groups, groups can be deleted).

From the tool's definition Tool description states 'Add a contact to a group. Creates the group if it doesn't exist.' The verbs 'add' and 'creates' indicate reversible data modification operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_to_group Rate-limited

add_to_group 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": {
    "add_to_group": {
      "limits": [
        {
          "counter": "add_to_group_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 add_to_group

What does the add_to_group tool do? +

Add a contact to a group. Creates the group if it doesn't exist. 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 add_to_group? +

Register the Nexus Core MCP server in PolicyLayer and add a rule for add_to_group: 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 add_to_group? +

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

Can I rate-limit add_to_group? +

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

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

add_to_group 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.