tools-template-render · Home Assistant MCP Server MCP

WHAT IT DOES

What tools-template-render does on Home Assistant MCP Server

AI agents invoke tools-template-render to trigger actions in Home Assistant MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why tools-template-render needs a policy

Rendering Jinja2 templates is an execution operation — it runs arbitrary template code with access to the Home Assistant state machine. While it may primarily read state, Jinja2 templates can invoke functions, perform calculations, and potentially trigger side effects depending on what Home Assistant exposes. This qualifies as Execute rather than Read due to the arbitrary code execution nature of template rendering.

From the tool's definition 'Render a Home Assistant template. Templates use the Jinja2 template engine and can access the Home Assistant state machine'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

tools-template-render Rate-limited

tools-template-render stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "tools-template-render": {
      "limits": [
        {
          "counter": "tools-template-render_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about tools-template-render

What does the tools-template-render tool do? +

Render a Home Assistant template. Templates use the Jinja2 template engine and can access the Home Assistant state machine, enabling dynamic values and calculations based on entity states. It is categorised as a Execute tool in the Home Assistant MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on tools-template-render? +

Register the Home Assistant MCP Server MCP server in PolicyLayer and add a rule for tools-template-render: 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 Home Assistant MCP Server. Nothing to install.

What risk level is tools-template-render? +

tools-template-render is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit tools-template-render? +

Yes. Add a rate_limit block to the tools-template-render 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 tools-template-render completely? +

Set action: deny in the PolicyLayer policy for tools-template-render. 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 tools-template-render? +

tools-template-render is provided by the Home Assistant MCP Server MCP server (oleander/home-assistant-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.