save_file · Nav MCP: Risk & Policy

WHAT IT DOES

What save_file does on Navmcp

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

WHY IT NEEDS A POLICY

Why save_file needs a policy

The tool appears to create or modify files based on its name. Without a description, confidence is reduced, but the name is explicit and consistent with the server's documented capabilities (web content extraction and file handling). This is a Write operation (reversible file creation/modification) rather than Destructive since it doesn't inherently delete or overwrite existing data irreversibly.

From the tool's definition Tool named 'save_file' with empty description on a browser automation server. The name indicates file creation/modification capability. Context of sibling tools (download_pdfs, fetch_and_save_url) confirms this server performs file I/O operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

save_file Rate-limited

save_file 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": {
    "save_file": {
      "limits": [
        {
          "counter": "save_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about save_file

What does the save_file tool do? +

save_file. It is categorised as a Write tool in the Navmcp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on save_file? +

Register the Nav MCP server in PolicyLayer and add a rule for save_file: 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 Navmcp. Nothing to install.

What risk level is save_file? +

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

Can I rate-limit save_file? +

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

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

save_file is provided by the Nav MCP server (jianlins/navmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.