list_classes

THE RISK

Low Risk

Why list_classes needs a policy

This tool retrieves and displays information about available CSS class names and patterns. It performs a discovery operation that does not modify, delete, or execute anything. It has no destructive, financial, or code execution capabilities. The blast radius of misuse is minimal—an AI agent listing available classes cannot cause harm or unexpected side effects.

From the tool's definition Tool description states 'List all available semantic class names' and 'Use this to discover available patterns.' The verb 'list' is a read-only query operation with no side effects.

Documented attack patterns abuse exactly the kind of access list_classes gives an agent:

POLICY

How to control list_classes

PolicyLayer is an MCP gateway — it sits between your AI agents and Classmcp, and nothing reaches the server without passing your rules. This is the rule we recommend for list_classes:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_classes": {}
  }
}

list_classes is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Classmcp — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

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EXPLORE

Related tools and policies

More Classmcp tools

Execute reload_config Reload custom patterns from the config file (.classmcp.json). Use this after modifying you Write generate_css Generate CSS that defines all semantic classes. Add this to your project Write set_framework Set the CSS framework to use for all subsequent operations. Choose based on your project Read get_class Get the full utility classes for a semantic class name. Returns the CSS classes you should Read get_component Get a complete HTML component example using semantic classes. Great for seeing how classes Read get_ssr_info Get SSR/hydration safety information for a class pattern. Use this when building SSR/Next. Read list_custom_patterns List all custom (user-defined) patterns loaded from your config file. Read list_frameworks List all available CSS frameworks and their statistics.

All 10 Classmcp tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_classes

What does the list_classes tool do? +

List all available semantic class names, optionally filtered by category. Use this to discover available patterns. It is categorised as a Read tool in the Classmcp MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_classes? +

Register the Class MCP server in PolicyLayer and add a rule for list_classes: 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 Classmcp. Nothing to install.

What risk level is list_classes? +

list_classes is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_classes? +

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

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

list_classes is provided by the Class MCP server (thedecipherist/classmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Classmcp tool call.

Start from Classmcp, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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