list_principles

THE RISK

Low Risk

Why list_principles needs a policy

This tool retrieves configuration information about principles without modifying, executing, or deleting anything. It is a straightforward read operation on stored data. The severity is low because even if misused by an AI agent, it only exposes configuration metadata without capability to alter system state or access sensitive operational data.

From the tool's definition Tool name 'list_principles' and description 'List your configured principles' indicate a retrieval operation with no side effects. The verb 'List' is characteristic of Read operations that query or retrieve data.

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

POLICY

How to control list_principles

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

policy.json

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

list_principles 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 Brain — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More Brain tools

Read bob_dropped Inspect what L1 filtered out. Optional reason filter (e.g. 'cc:build-log-paste'). Read alignment_check Check if a decision aligns with your principles. Read bob_conversations_by_date List all conversations active on a given date (YYYY-MM-DD). For each Read bob_health Report the state of Bob's local memory. Use this first if you don't know Read bob_recent Most recent turns within the last hours. Filter by src and/or role. Read bob_search bob_search Read bob_thinking_trajectory Chronological pass on a topic — first mention to most recent. Shows how Read bob_tunnel_state Reconstruct work-in-progress on a domain/topic. Returns the most recent

All 34 Brain 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_principles

What does the list_principles tool do? +

List your configured principles. It is categorised as a Read tool in the Brain MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_principles? +

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

What risk level is list_principles? +

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

Can I rate-limit list_principles? +

Yes. Add a rate_limit block to the list_principles 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_principles completely? +

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

list_principles is provided by the Brain MCP server (mordechaipotash/brain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Brain tool call.

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

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