ynab_create_transaction · YNAB MCP Server MCP: Risk & Policy

WHAT IT DOES

What ynab_create_transaction does on YNAB MCP Server

AI agents use ynab_create_transaction to create or update resources in YNAB MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your YNAB MCP Server environment.

WHY IT NEEDS A POLICY

Why ynab_create_transaction needs a policy

This tool creates new transaction records in a financial management system (YNAB), which modifies financial data reversibly. It does not move money between accounts (that is ynab_move_money), nor does it delete data (Destructive), nor does it directly process payments or financial obligations (Financial category reserved for actual money transfer, payments, trades, subscriptions).

From the tool's definition Tool name 'ynab_create_transaction' and description 'Create a new transaction' indicate the creation of new financial records.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ynab_create_transaction Rate-limited

ynab_create_transaction stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "ynab_create_transaction": {
      "limits": [
        {
          "counter": "ynab_create_transaction_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches YNAB MCP Server, so you can run agents against it safely.

FAQ

Questions about ynab_create_transaction

What does the ynab_create_transaction tool do? +

Create a new transaction. Use negative amounts for spending, positive for income. It is categorised as a Write tool in the YNAB MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on ynab_create_transaction? +

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

What risk level is ynab_create_transaction? +

ynab_create_transaction is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit ynab_create_transaction? +

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

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

ynab_create_transaction is provided by the YNAB MCP Server MCP server (wgdevelopment/ynab-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.