lsp_format_document · Lsp MCP: Risk & Policy

WHAT IT DOES

What lsp_format_document does on Lsp

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

WHY IT NEEDS A POLICY

Why lsp_format_document needs a policy

This tool creates or modifies file content reversibly by reformatting code according to project standards (prettier, eslint, etc.). When apply=true, it writes changes to disk. This is a Write operation because the changes are reversible (formatting can be undone or re-run), not destructive.

From the tool's definition 'Format a file according to project style settings' and 'Set apply=true to write changes' — the tool modifies file content by applying formatting rules when apply=true is set.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

lsp_format_document Rate-limited

lsp_format_document 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": {
    "lsp_format_document": {
      "limits": [
        {
          "counter": "lsp_format_document_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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

FAQ

Questions about lsp_format_document

What does the lsp_format_document tool do? +

Format a file according to project style settings (prettier, eslint, etc.). Use after making edits to ensure consistent formatting. Set apply=true to write changes. It is categorised as a Write tool in the Lsp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on lsp_format_document? +

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

What risk level is lsp_format_document? +

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

Can I rate-limit lsp_format_document? +

Yes. Add a rate_limit block to the lsp_format_document 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_format_document completely? +

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

lsp_format_document is provided by the Lsp MCP server (lsp-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.