km_add_calculation

THE RISK

Medium Risk

Why km_add_calculation needs a policy

This tool adds an action to a macro that sets a variable to a calculated value. It modifies the macro definition (Write), but the description is incomplete. The core operation is writing/creating a new action within a macro, not executing code directly. Severity is medium because modifying macros could have downstream effects when those macros run, but the tool itself is a write operation.

From the tool's definition 'Add an action to set a variable to the result of a calculation'

Documented attack patterns abuse exactly the kind of access km_add_calculation gives an agent:

POLICY

How to control km_add_calculation

PolicyLayer is an MCP gateway — it sits between your AI agents and Keyboard Maestro, and nothing reaches the server without passing your rules. This is the rule we recommend for km_add_calculation:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "km_add_calculation": {
      "limits": [
        {
          "counter": "km_add_calculation_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

km_add_calculation 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.

Create a free account and register Keyboard Maestro — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Keyboard Maestro tools

Destructive km_delete_action Delete a specific action from a macro. Actions are 1-indexed. WARNING: This cannot be undo Destructive km_delete_macro Delete a macro by name or UID. WARNING: This cannot be undone! Destructive km_delete_trigger Delete a trigger from a macro. Triggers are 1-indexed. Destructive km_manage_group Manage macro groups (create, delete, toggle, list). Execute km_run_macro Execute a macro by name or UID. Execute km_add_execute_macro Add an action to execute another macro. Execute km_add_shell_script Add an action to execute a shell script. Write km_search_replace_action Search and replace text within a specific action in a macro. Useful for fixing typos or up

All 34 Keyboard Maestro tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about km_add_calculation

What does the km_add_calculation tool do? +

Add an action to set a variable to the result of a calculation (e.g.,. It is categorised as a Write tool in the Keyboard Maestro MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on km_add_calculation? +

Register the Keyboard Maestro MCP server in PolicyLayer and add a rule for km_add_calculation: 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 Keyboard Maestro. Nothing to install.

What risk level is km_add_calculation? +

km_add_calculation is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit km_add_calculation? +

Yes. Add a rate_limit block to the km_add_calculation 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.

How do I block km_add_calculation completely? +

Set action: deny in the PolicyLayer policy for km_add_calculation. 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.

What MCP server provides km_add_calculation? +

km_add_calculation is provided by the Keyboard Maestro MCP server (saihgupr/keyboard-maestro-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Keyboard Maestro tool call.

Start from Keyboard Maestro, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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