Create a new transaction in Monarch Money. Args: date: Transaction date in YYYY-MM-DD format account_id: The account ID to add the transaction to amount: Transaction amount (positive for income, negative for expenses) merchant_name: Merchant or payee name category_id: Category ID for the transact...
AI agents use create_transaction to create or update resources in Monarch — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Monarch environment.
This tool creates new financial records (transactions) in a money management system, which is a reversible write operation. It does not move actual money (Financial category) nor is it destructive/irreversible. However, it has high severity because creating fraudulent or incorrect transactions in a financial application could cause significant confusion, incorrect reporting, and require manual correction by the user.
From the tool's definition Tool description states "Create a new transaction in Monarch Money" with parameters for date, account_id, amount, merchant_name, category_id, and notes. The update_balance parameter indicates it can modify account state.
Documented attack patterns abuse exactly the kind of access create_transaction gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Monarch, and nothing reaches the server without passing your rules. This is the rule we recommend for create_transaction:
{
"version": "1",
"default": "deny",
"tools": {
"create_transaction": {
"limits": [
{
"counter": "create_transaction_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}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.
Free to start. No card required.
Create a new transaction in Monarch Money. Args: date: Transaction date in YYYY-MM-DD format account_id: The account ID to add the transaction to amount: Transaction amount (positive for income, negative for expenses) merchant_name: Merchant or payee name category_id: Category ID for the transaction notes: Optional notes for the transaction update_balance: Whether to update the account balance (default: false). It is categorised as a Write tool in the Monarch MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Monarch MCP server in PolicyLayer and add a rule for 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 Monarch. Nothing to install.
create_transaction is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the 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.
Set action: deny in the PolicyLayer policy for 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.
create_transaction is provided by the Monarch MCP server (robcerda/monarch-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 50 Monarch tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
50 Monarch tools catalogued and risk-classified — across an index of 42,500+ MCP servers.