add_expense

A write tool on the Agent Jail MCP server.

SERVERAgent Jail SOURCEidiscoord13-sketch/agent-jail-mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/agent-jail-mcp/add-expense.md

WHAT IT DOES

What add_expense does on Agent Jail

AI agents use add_expense to create or update resources in Agent Jail, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Agent Jail environment.

RISK

Why add_expense is rated Medium

The tool creates new expense entries in a financial tracking system, which is reversible via 'delete_expense'. While this modifies financial records, it does not move money directly (category: Financial) or irreversibly destroy data (category: Destructive).

From the tool's definition Tool name 'add_expense' combined with server context (Expense Tracker managing expenses through MCP) indicates creation of new expense records.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs add_expense safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Agent Jail, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For add_expense, this is the rule to start with:

add_expense Rate-limited

add_expense 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": {
    "add_expense": {
      "limits": [
        {
          "counter": "add_expense_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Agent Jail, apply this rule, and every add_expense call is checked against it from then on.

FAQ

Questions about add_expense

What does the add_expense tool do? +

add_expense is a write tool on the Agent Jail MCP server. It is categorised as a Write tool in the Agent Jail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_expense? +

Register the Agent Jail MCP server in PolicyLayer and add a rule for add_expense: 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 Agent Jail. Nothing to install.

What risk level is add_expense? +

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

Can I rate-limit add_expense? +

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

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

add_expense is provided by the Agent Jail MCP server (idiscoord13-sketch/agent-jail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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