lookup-entity-by-id

THE RISK

Low Risk

Why lookup-entity-by-id needs a policy

This tool performs a lookup operation that retrieves and queries financial data (account details, category names, payee information) without side effects. While the context is sensitive financial data, the tool itself only reads information.

From the tool's definition Tool description states 'Look up the name and details of a specific account, category, or payee by its ID.' The action is retrieval of existing data with no modification, deletion, or execution of external operations.

Documented attack patterns abuse exactly the kind of access lookup-entity-by-id gives an agent:

POLICY

How to control lookup-entity-by-id

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 lookup-entity-by-id:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "lookup-entity-by-id": {}
  }
}

lookup-entity-by-id 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 →

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EXPLORE

Related tools and policies

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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 lookup-entity-by-id

What does the lookup-entity-by-id tool do? +

Look up the name and details of a specific account, category, or payee by its ID. A utility for when you have an ID but need the full context. 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 lookup-entity-by-id? +

Register the You Need A Budget (YNAB) MCP server in PolicyLayer and add a rule for lookup-entity-by-id: 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 lookup-entity-by-id? +

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

Can I rate-limit lookup-entity-by-id? +

Yes. Add a rate_limit block to the lookup-entity-by-id 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 lookup-entity-by-id completely? +

Set action: deny in the PolicyLayer policy for lookup-entity-by-id. 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 lookup-entity-by-id? +

lookup-entity-by-id 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 →