add_host_tag · Defined MCP: Risk & Policy

WHAT IT DOES

What add_host_tag does on Defined

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

WHY IT NEEDS A POLICY

Why add_host_tag needs a policy

Adding a tag to a host creates or modifies data in a reversible manner (tags can be removed). This is a Write operation rather than Execute because it doesn't trigger code execution or external operations dependent on arguments; it simply updates host attributes.

From the tool's definition Tool description states 'Add a tag to a host. Preserves existing tags.' — this modifies host metadata by adding a tag, a reversible operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_host_tag Rate-limited

add_host_tag 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_host_tag": {
      "limits": [
        {
          "counter": "add_host_tag_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 Defined, so you can run agents against it safely.

FAQ

Questions about add_host_tag

What does the add_host_tag tool do? +

Add a tag to a host. Preserves existing tags. It is categorised as a Write tool in the Defined 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_host_tag? +

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

What risk level is add_host_tag? +

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

Can I rate-limit add_host_tag? +

Yes. Add a rate_limit block to the add_host_tag 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_host_tag completely? +

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

add_host_tag is provided by the Defined MCP server (quickvm/defined-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.