check_index

THE RISK

Low Risk

Why check_index needs a policy

This tool performs read-only diagnostics on the index metadata and state. It surfaces problems but does not modify, delete, or execute arbitrary operations. The blast radius of misuse is minimal; an agent calling this repeatedly would only generate redundant status checks.

From the tool's definition The tool 'check_index' verifies index health and detects issues—it queries the state of the index for missing files, orphaned vectors, and dimension mismatches.

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

POLICY

How to control check_index

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

policy.json

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

check_index 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 MCP Codebase Index — 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

Related tools and policies

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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 check_index

What does the check_index tool do? +

Verify index health and detect issues like missing files, orphaned vectors, and dimension mismatches. It is categorised as a Read tool in the MCP Codebase Index MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on check_index? +

Register the MCP Codebase Index MCP server in PolicyLayer and add a rule for check_index: 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 MCP Codebase Index. Nothing to install.

What risk level is check_index? +

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

Can I rate-limit check_index? +

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

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

check_index is provided by the MCP Codebase Index MCP server (ngotaico/mcp-codebase-index). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Codebase Index tool call.

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

CHECK YOUR STACK →