Update an existing transaction in Monarch Money. Args: transaction_id: The ID of the transaction to update category_id: New category ID merchant_name: New merchant or payee name goal_id: Goal ID to associate with the transaction amount: New transaction amount date: New transaction date in YYYY-MM...
AI agents use update_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 or modifies data reversibly without deleting it. While it affects financial records (transactions), it does not move money or create financial obligations (Financial category), and does not irreversibly delete data (Destructive category).
From the tool's definition Tool description states it can 'Update an existing transaction', modifying fields like category_id, merchant_name, goal_id, amount, date, hide_from_reports, needs_review, and notes. These are reversible changes to transaction metadata and properties.
Documented attack patterns abuse exactly the kind of access update_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 update_transaction:
{
"version": "1",
"default": "deny",
"tools": {
"update_transaction": {
"limits": [
{
"counter": "update_transaction_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_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.
Update an existing transaction in Monarch Money. Args: transaction_id: The ID of the transaction to update category_id: New category ID merchant_name: New merchant or payee name goal_id: Goal ID to associate with the transaction amount: New transaction amount date: New transaction date in YYYY-MM-DD format hide_from_reports: Whether to hide this transaction from reports needs_review: Whether this transaction needs review notes: Notes for the transaction. 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 update_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.
update_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 update_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 update_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.
update_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.