index_build · TOOL4LM MCP: Risk & Policy

WHAT IT DOES

What index_build does on TOOL4LM

AI agents invoke index_build to trigger actions in TOOL4LM. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why index_build needs a policy

Building an index is an active operation that processes data and creates new structures, going beyond simple reads. It triggers external computation and likely writes index data to disk. The description is uninformative (just says 'Alias of index.build'), which lowers confidence.

From the tool's definition Tool name 'index_build' (alias of 'index.build') suggests building/constructing an index, which involves processing documents and executing an indexing operation

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

index_build Rate-limited

index_build stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "index_build": {
      "limits": [
        {
          "counter": "index_build_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches TOOL4LM, so you can run agents against it safely.

FAQ

Questions about index_build

What does the index_build tool do? +

Alias of index.build. It is categorised as a Execute tool in the TOOL4LM MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on index_build? +

Register the TOOL4LM MCP server in PolicyLayer and add a rule for index_build: 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 TOOL4LM. Nothing to install.

What risk level is index_build? +

index_build is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit index_build? +

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

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

index_build is provided by the TOOL4LM MCP server (khanhs-234/tool4lm). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.