save_screenshot · Formlabs Local MCP: Risk & Policy

WHAT IT DOES

What save_screenshot does on Formlabs Local

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

WHY IT NEEDS A POLICY

Why save_screenshot needs a policy

This tool creates/writes a new file (PNG image) to the filesystem. While it does not modify existing data or have irreversible destructive effects, it does perform a persistent write operation. The severity is medium because: (1) uncontrolled use could fill disk space or overwrite files if the path already exists, and (2) the absolute path parameter introduces some risk if an attacker can control the destination.

From the tool's definition The tool 'save_screenshot' creates a new PNG file at a specified absolute path, as indicated by 'Save a PNG screenshot of the scene to the given absolute path.' This is a file creation operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

save_screenshot Rate-limited

save_screenshot 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_screenshot": {
      "limits": [
        {
          "counter": "save_screenshot_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 Formlabs Local, so you can run agents against it safely.

FAQ

Questions about save_screenshot

What does the save_screenshot tool do? +

Save a PNG screenshot of the scene to the given absolute path. It is categorised as a Write tool in the Formlabs Local 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_screenshot? +

Register the Formlabs Local MCP server in PolicyLayer and add a rule for save_screenshot: 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 Formlabs Local. Nothing to install.

What risk level is save_screenshot? +

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

Can I rate-limit save_screenshot? +

Yes. Add a rate_limit block to the save_screenshot 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_screenshot completely? +

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

save_screenshot is provided by the Formlabs Local MCP server (mkebiclioglu/formlabs-local-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.