AI agents call list_months to retrieve information from Ynab without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and displays budget month information (income, budgeted amounts, activity, ready to assign) without creating, modifying, or deleting any data. It is a pure read operation that queries existing budget state. While the server overall is Financial in scope, this specific tool performs no financial transactions or commitments—it only displays data.
From the tool's definition Tool name 'list_months' and description 'List all budget months for a budget, showing income, budgeted, activity, and ready to assign' indicate retrieval of financial data with no modifications or side effects.
Attacks that exploit this kind of access
[1 API call] List all budget months for a budget, showing income, budgeted, activity, and ready to assign. It is categorised as a Read tool in the Ynab MCP Server, which means it retrieves data without modifying state.
Register the Ynab MCP server in PolicyLayer and add a rule for list_months: 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. Nothing to install.
list_months is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_months 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.
Set action: deny in the PolicyLayer policy for list_months. 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.
list_months is provided by the Ynab MCP server (justmytwospence/ynab-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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