list_by_category

THE RISK

Low Risk

Why list_by_category needs a policy

This tool retrieves and displays information about available endpoints organized by category. It has no side effects, does not execute code or commands, does not modify state, and does not control robot hardware. It is purely informational and read-only in nature, making it the lowest-risk category.

From the tool's definition Tool name is 'list_by_category' and description states it 'List all endpoints in a specific functional category' — a straightforward retrieval and enumeration operation with no modification or execution of robot control.

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

POLICY

How to control list_by_category

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

policy.json

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

list_by_category 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 Opentrons MCP Server — 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More Opentrons MCP Server tools

Execute control_run Control run execution (play, pause, stop, resume) Execute home_robot Home robot axes or specific pipette Execute poll_error_endpoint_and_fix Fetch specific JSON error report and automatically fix protocols Execute create_run Create a new protocol run on the robot Write control_lights Turn robot lights on or off Write upload_protocol Upload a protocol file to an Opentrons robot Read get_api_overview Get high-level overview of the Opentrons HTTP API structure and capabilities Read get_endpoint_details Get comprehensive details about a specific API endpoint

All 14 Opentrons MCP Server 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_by_category

What does the list_by_category tool do? +

List all endpoints in a specific functional category. It is categorised as a Read tool in the Opentrons MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_by_category? +

Register the Opentrons MCP Server MCP server in PolicyLayer and add a rule for list_by_category: 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 Opentrons MCP Server. Nothing to install.

What risk level is list_by_category? +

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

Can I rate-limit list_by_category? +

Yes. Add a rate_limit block to the list_by_category 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_by_category completely? +

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

list_by_category is provided by the Opentrons MCP Server MCP server (yerbymatey/opentrons-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Opentrons MCP Server tool call.

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

CHECK YOUR STACK →