ha_update_entity_registry · Hass MCP: Risk & Policy

WHAT IT DOES

What ha_update_entity_registry does on Hass

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

WHY IT NEEDS A POLICY

Why ha_update_entity_registry needs a policy

This tool modifies Home Assistant's entity registry by changing entity metadata (name, entity_id, area assignment). These are reversible configuration changes that alter system state without deleting data or executing arbitrary operations.

From the tool's definition Tool name 'ha_update_entity_registry' and description 'Update an entity registry entry (e.g., change name, entity_id, or area_id)' indicate modification of configuration data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ha_update_entity_registry Rate-limited

ha_update_entity_registry 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": {
    "ha_update_entity_registry": {
      "limits": [
        {
          "counter": "ha_update_entity_registry_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Hass, so you can run agents against it safely.

FAQ

Questions about ha_update_entity_registry

What does the ha_update_entity_registry tool do? +

Update an entity registry entry (e.g., change name, entity_id, or area_id). It is categorised as a Write tool in the Hass MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on ha_update_entity_registry? +

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

What risk level is ha_update_entity_registry? +

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

Can I rate-limit ha_update_entity_registry? +

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

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

ha_update_entity_registry is provided by the Hass MCP server (thewhykiki/hass-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.