Set tags on a transaction. Note: This REPLACES all existing tags on the transaction. To add a tag, include both existing and new tag IDs. To remove all tags, pass an empty list. Args: transaction_id: The ID of the transaction to tag tag_ids: List of tag IDs to apply (use get_tags to find IDs) Ret...
AI agents use set_transaction_tags 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 transaction metadata by updating tags, which is a reversible write operation. While it replaces existing tags (potentially destructive to the tag set itself), the core transaction data remains intact and the operation can be undone by re-setting tags. This fits the Write category (creates or modifies data reversibly) rather than Destructive.
From the tool's definition Tool description states it 'REPLACES all existing tags on a transaction' and accepts transaction_id and tag_ids as arguments to modify transaction metadata.
Documented attack patterns abuse exactly the kind of access set_transaction_tags 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 set_transaction_tags:
{
"version": "1",
"default": "deny",
"tools": {
"set_transaction_tags": {
"limits": [
{
"counter": "set_transaction_tags_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_transaction_tags 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.
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Set tags on a transaction. Note: This REPLACES all existing tags on the transaction. To add a tag, include both existing and new tag IDs. To remove all tags, pass an empty list. Args: transaction_id: The ID of the transaction to tag tag_ids: List of tag IDs to apply (use get_tags to find IDs) Returns: Updated transaction details. 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 set_transaction_tags: 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.
set_transaction_tags 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 set_transaction_tags 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 set_transaction_tags. 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.
set_transaction_tags 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.