mcp-ffmpeg

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set_video_audio_track_codec

Change the audio codec of a video while preserving the video stream. Specify input path, output path, and target audio codec to convert.

Instructions

Sets the audio codec of a video's audio track, attempting to copy the video stream.

Args: input_video_path: Path to the source video file. output_video_path: Path to save the video with the new audio codec. audio_codec: Target audio codec (e.g., 'aac', 'mp3'). Returns: A status message indicating success or failure.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "input_video_path": "<input_video_path>",
      "output_video_path": "<output_video_path>",
      "audio_codec": "<audio_codec>"
    },
    "name": "set_video_audio_track_codec"
  }
}

Input Schema

Name	Required	Description	Default
`audio_codec`	Yes
`input_video_path`	Yes
`output_video_path`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 11, 2026

TDQS

A3.7/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are present, so the description must carry the full burden of behavioral disclosure. It does mention 'attempting to copy the video stream,' which is a notable behavioral trait, and states that it returns a status message. However, it fails to specify failure behavior, whether the output file overwrites existing files, or if the input is preserved, leaving important safety information undisclosed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise and well-structured: a one-sentence summary, an Args list, and a Returns note. Each section provides necessary information without redundancy or filler, earning its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple tool with three string parameters and an output schema, the description adequately covers the main purpose, parameter roles, and return value. However, it omits important context such as which audio track is targeted (e.g., first track), supported codec limitations, or how failures are handled. Given the abundance of closely related sibling tools, this lack of edge-case detail makes it only minimally complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has no descriptions for any parameters, so the description compensates by listing all three parameters with brief role explanations. For audio_codec, it provides examples ('aac', 'mp3'), adding concrete meaning beyond the schema. It doesn't mention constraints or defaults, but the basic descriptions improve usability.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function with a specific verb and resource: 'Sets the audio codec of a video's audio track.' It distinguishes from sibling tools like set_video_audio_track_bitrate and set_video_audio_track_sample_rate by focusing on codec. The phrase 'attempting to copy the video stream' adds useful context about its behavior.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no explicit guidance on when to use this tool versus alternatives. It does not mention prerequisites, exclusions, or contrast with sibling tools such as convert_audio_format or set_audio_sample_rate. Usage must be inferred entirely from the function name and purpose statement.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.