merge · Ffmpeg MCP: Risk & Policy

WHAT IT DOES

What merge does on Ffmpeg

AI agents use merge 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 merge needs a policy

The merge tool creates a new combined media file from multiple inputs. This is a Write operation as it produces a new file without irreversibly destroying the originals. Severity is medium because misuse could overwrite existing files or produce large unintended outputs, but the operation is generally reversible.

From the tool's definition Concatenate multiple media files into one. Supports same-codec fast concat or cross-codec re-encoding.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

merge Rate-limited

merge 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": {
    "merge": {
      "limits": [
        {
          "counter": "merge_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 merge

What does the merge tool do? +

Concatenate multiple media files into one. Supports same-codec fast concat or cross-codec re-encoding. 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 merge? +

Register the Ffmpeg MCP server in PolicyLayer and add a rule for merge: 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 merge? +

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

Can I rate-limit merge? +

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

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

merge 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.