Split a transaction into multiple parts with different categories/merchants. The sum of all split amounts must equal the original transaction amount. Pass an empty list to remove all splits and restore the original transaction. Args: transaction_id: The ID of the transaction to split splits: List...
AI agents use split_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 modifies an existing transaction by splitting it into parts or restoring it to its original state. It alters financial data but does not move money or delete records irreversibly — splits can be removed and restored. This is a reversible modification, placing it in the Write category.
From the tool's definition Split a transaction into multiple parts with different categories/merchants. Pass an empty list to remove all splits and restore the original transaction.
Documented attack patterns abuse exactly the kind of access split_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 split_transaction:
{
"version": "1",
"default": "deny",
"tools": {
"split_transaction": {
"limits": [
{
"counter": "split_transaction_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}split_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.
Split a transaction into multiple parts with different categories/merchants. The sum of all split amounts must equal the original transaction amount. Pass an empty list to remove all splits and restore the original transaction. Args: transaction_id: The ID of the transaction to split splits: List of split objects. Each split should have: - amount: The amount for this split (negative for expenses, positive for income) - categoryId: (optional) The category ID for this split - merchantName: (optional) The merchant name for this split Returns: The updated split information 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 split_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.
split_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 split_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 split_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.
split_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.