create_thumbnail · Claude File Management Server MCP

WHAT IT DOES

What create_thumbnail does on Claude File Management Server

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

WHY IT NEEDS A POLICY

Why create_thumbnail needs a policy

The tool generates a new thumbnail image artifact (write operation) from an existing image source. This is reversible and non-destructive—the original image remains unchanged, and the thumbnail can be deleted or regenerated. It has no side effects on the system beyond creating a derived image file.

From the tool's definition Tool creates a new thumbnail image file and returns it as base64-encoded PNG, which is a reversible write operation that generates new image data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_thumbnail Rate-limited

create_thumbnail 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": {
    "create_thumbnail": {
      "limits": [
        {
          "counter": "create_thumbnail_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 Claude File Management Server, so you can run agents against it safely.

FAQ

Questions about create_thumbnail

What does the create_thumbnail tool do? +

Create a thumbnail from an image and return as base64-encoded PNG. It is categorised as a Write tool in the Claude File Management Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_thumbnail? +

Register the Claude File Management Server MCP server in PolicyLayer and add a rule for create_thumbnail: 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 Claude File Management Server. Nothing to install.

What risk level is create_thumbnail? +

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

Can I rate-limit create_thumbnail? +

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

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

create_thumbnail is provided by the Claude File Management Server MCP server (vipin1000/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.