subtitle · Ffmpeg MCP: Risk & Policy

WHAT IT DOES

What subtitle does on Ffmpeg

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

WHY IT NEEDS A POLICY

Why subtitle needs a policy

This tool creates or modifies video files by adding subtitle data. While it produces output files rather than destructively overwriting originals (the typical use case involves creating new video outputs), it is fundamentally a Write operation that alters media content. It does not execute arbitrary code or trigger external operations beyond FFmpeg's documented subtitle-addition functionality, so it is not Execute.

From the tool's definition The tool 'Add subtitles to video - burn into video (hardcode) or add as selectable soft track' modifies video files by either permanently embedding subtitles or adding subtitle tracks.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

subtitle Rate-limited

subtitle 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": {
    "subtitle": {
      "limits": [
        {
          "counter": "subtitle_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 Ffmpeg, so you can run agents against it safely.

FAQ

Questions about subtitle

What does the subtitle tool do? +

Add subtitles to video - burn into video (hardcode) or add as selectable soft track. Supports SRT, ASS, VTT. It is categorised as a Write tool in the Ffmpeg MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on subtitle? +

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

What risk level is subtitle? +

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

Can I rate-limit subtitle? +

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

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

subtitle is provided by the Ffmpeg MCP server (yuan66-hub/ffmpeg-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.