estimate_cost

THE RISK

Low Risk

Why estimate_cost needs a policy

This tool retrieves and analyzes token usage metrics to produce a cost estimate. It performs no side effects, creates no resources, executes no code or commands, and causes no data loss. It is purely informational, fitting the Read category definition of 'retrieves or queries data; no side effects'.

From the tool's definition Tool name 'estimate_cost' and description 'Estimate API costs based on token usage across all conversations' indicate a calculation/estimation operation that queries existing data without modifying, deleting, or executing external operations.

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

POLICY

How to control estimate_cost

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "estimate_cost": {}
  }
}

estimate_cost is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about estimate_cost

What does the estimate_cost tool do? +

Estimate API costs based on token usage across all conversations. It is categorised as a Read tool in the Claude Code Toolkit MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on estimate_cost? +

Register the Claude Code Toolkit MCP server in PolicyLayer and add a rule for estimate_cost: 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 Claude Code Toolkit. Nothing to install.

What risk level is estimate_cost? +

estimate_cost is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit estimate_cost? +

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

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

estimate_cost is provided by the Claude Code Toolkit MCP server (asifkibria/claude-code-toolkit). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Claude Code Toolkit tool call.

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

CHECK YOUR STACK →