firefly_create_category · Firefly III MCP Server MCP

WHAT IT DOES

What firefly_create_category does on Firefly III MCP Server

AI agents use firefly_create_category to create or update resources in Firefly III MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Firefly III MCP Server environment.

WHY IT NEEDS A POLICY

Why firefly_create_category needs a policy

This tool creates financial metadata (a transaction category) rather than moving money or executing arbitrary code. While it modifies the financial system's state, category creation is a reversible write operation with minimal blast radius. It does not commit financial obligations, execute commands, or destroy data.

From the tool's definition Tool name 'firefly_create_category' and description 'Create a new transaction category' indicate data creation. The action creates a new category record in Firefly III, which is reversible (categories can be deleted or modified).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

firefly_create_category Rate-limited

firefly_create_category 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Firefly III MCP Server, so you can run agents against it safely.

FAQ

Questions about firefly_create_category

What does the firefly_create_category tool do? +

Create a new transaction category. It is categorised as a Write tool in the Firefly III MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on firefly_create_category? +

Register the Firefly III MCP Server MCP server in PolicyLayer and add a rule for firefly_create_category: 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 Firefly III MCP Server. Nothing to install.

What risk level is firefly_create_category? +

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

Can I rate-limit firefly_create_category? +

Yes. Add a rate_limit block to the firefly_create_category 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 firefly_create_category completely? +

Set action: deny in the PolicyLayer policy for firefly_create_category. 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 firefly_create_category? +

firefly_create_category is provided by the Firefly III MCP Server MCP server (przbadu/firefly-iii-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.