lsp_diagnostics · LocalAnt MCP: Risk & Policy

WHAT IT DOES

What lsp_diagnostics does on LocalAnt

AI agents invoke lsp_diagnostics to trigger actions in LocalAnt. 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 lsp_diagnostics needs a policy

This tool executes the TypeScript compiler (tsc) as a subprocess. Although the --noEmit flag prevents file writes and the operation is read-only in intent (diagnostics are informational), the act of running a compiler process on arbitrary project paths qualifies as Execute under the MCP taxonomy—it triggers external operations whose side effects depend on the arguments (project path).

From the tool's definition Tool runs TypeScript compiler diagnostics (tsc --noEmit) on a project path, which executes an external command/process. The description explicitly states it 'Run[s]' diagnostics, indicating code execution.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

lsp_diagnostics Rate-limited

lsp_diagnostics 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": {
    "lsp_diagnostics": {
      "limits": [
        {
          "counter": "lsp_diagnostics_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 LocalAnt, so you can run agents against it safely.

FAQ

Questions about lsp_diagnostics

What does the lsp_diagnostics tool do? +

Run TypeScript diagnostics (tsc --noEmit) for a project path. Falls back to install guidance if tsc is missing. It is categorised as a Execute tool in the LocalAnt MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on lsp_diagnostics? +

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

What risk level is lsp_diagnostics? +

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

Can I rate-limit lsp_diagnostics? +

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

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

lsp_diagnostics is provided by the LocalAnt MCP server (yuga-hashimoto/localant). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.