apply_yaml · K8s MCP: Risk & Policy

WHAT IT DOES

What apply_yaml does on K8s MCP

AI agents use apply_yaml to create or update resources in K8s MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your K8s MCP environment.

WHY IT NEEDS A POLICY

Why apply_yaml needs a policy

The tool creates or modifies Kubernetes resources through YAML application. While it can alter running infrastructure, it is reversible (resources can be re-applied or deleted). It does not irreversibly delete data (which would be Destructive) or execute arbitrary code within containers (which would be Execute). It is classified as Write due to its create/modify nature.

From the tool's definition Tool description states 'Apply Kubernetes resources from YAML content (upsert: create if missing, patch if exists)' — upsert operations create or modify resources reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

apply_yaml Rate-limited

apply_yaml 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": {
    "apply_yaml": {
      "limits": [
        {
          "counter": "apply_yaml_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 K8s MCP, so you can run agents against it safely.

FAQ

Questions about apply_yaml

What does the apply_yaml tool do? +

Apply Kubernetes resources from YAML content (upsert: create if missing, patch if exists). It is categorised as a Write tool in the K8s MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on apply_yaml? +

Register the K8s MCP server in PolicyLayer and add a rule for apply_yaml: 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 K8s MCP. Nothing to install.

What risk level is apply_yaml? +

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

Can I rate-limit apply_yaml? +

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

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

apply_yaml is provided by the K8s MCP server (rahul007-bit/k8s-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.