list-categories

THE RISK

Low Risk

Why list-categories needs a policy

This tool retrieves and enumerates budget category information without creating, modifying, deleting, or executing any operations. It is a read-only data retrieval function. While the server has broad financial access, this specific tool has minimal blast radius—it only exposes category metadata and budgeting structure, not sensitive transaction data or the ability to move money.

From the tool's definition Tool name 'list-categories' and description 'List all categories, groups, and their budgeting details for a given budget' indicate a query/retrieval operation with no modification of data.

Documented attack patterns abuse exactly the kind of access list-categories gives an agent:

POLICY

How to control list-categories

PolicyLayer is an MCP gateway — it sits between your AI agents and You Need A Budget (YNAB) MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for list-categories:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list-categories": {}
  }
}

list-categories 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 You Need A Budget (YNAB) MCP — 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 You Need A Budget (YNAB) MCP tools

Destructive bulk-manage-transactions Create, update, or delete multiple transactions at once. More efficient than making single Write manage-budgeted-amount Assign a budgeted amount to a category or move money between categories for a specific mon Write manage-financial-overview Get, update, or refresh a high-level financial overview. This is the best starting point f Write manage-payees Merge multiple payee names into a single name. Use this to clean up payee data, for exampl Write manage-scheduled-transaction Create, update, or delete a single scheduled (recurring) transaction. Use this to manage r Read get-month-info Get detailed budget information for a single month, including age of money and total amoun Read list-accounts List all accounts for a given budget. Useful for getting account IDs for other tools. Read list-budgets List all available YNAB budgets

All 14 You Need A Budget (YNAB) MCP 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-categories

What does the list-categories tool do? +

List all categories, groups, and their budgeting details for a given budget. It is categorised as a Read tool in the You Need A Budget (YNAB) MCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list-categories? +

Register the You Need A Budget (YNAB) MCP server in PolicyLayer and add a rule for list-categories: 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 You Need A Budget (YNAB) MCP. Nothing to install.

What risk level is list-categories? +

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

Can I rate-limit list-categories? +

Yes. Add a rate_limit block to the list-categories 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-categories completely? +

Set action: deny in the PolicyLayer policy for list-categories. 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-categories? +

list-categories is provided by the You Need A Budget (YNAB) MCP server (jtewen/ynab-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every You Need A Budget (YNAB) MCP tool call.

Start from You Need A Budget (YNAB) MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →