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mabh111111

FFmpeg Python MCP Server

by mabh111111

change_video_speed

Adjust video playback speed from slow motion to fast forward. Optionally preserve original audio pitch.

Instructions

改变视频播放速度

Args:
    input_path: 输入视频文件路径
    speed: 播放速度倍数(0.5=半速,1.0=原速,2.0=两倍速)
    output_path: 输出视频文件路径(可选)
    keep_audio_pitch: 是否保持音频音调不变

Returns:
    速度调整结果信息

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
input_pathYes
speedYes
output_pathNo
keep_audio_pitchNo
Behavior2/5

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

With no annotations present, the description carries full responsibility for behavioral disclosure. It does not explain whether the tool creates a new file or modifies the input, nor does it mention side effects like audio pitch preservation (though the parameter is listed). The response format is vague ('速度调整结果信息'), lacking detail on output behavior.

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 remarkably concise, consisting of a clear one-line purpose followed by a bulleted parameter list. Every sentence is functional with no redundant information, making it easy to parse quickly.

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?

The description covers the core parameters and returns a result message, but it omits practical details such as the default output path when 'output_path' is not provided, and it does not explain the relationship between speed and audio pitch behavior. Given the tool's simplicity, this is adequate but not exhaustive.

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 schema has 0% parameter descriptions, so the description adds critical meaning by explaining each parameter, e.g., 'speed' is a multiplier with examples (0.5, 1.0, 2.0) and 'keep_audio_pitch' is described as preserving audio pitch. This effectively compensates for the schema's lack of documentation.

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 '改变视频播放速度' clearly states the tool's function as changing video playback speed. This verb+resource description is specific and distinguishes it from sibling tools that perform other operations like compression, conversion, or cutting.

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 guidance on when to use this tool versus alternatives like 'cut_video_segment' or 'resize_video'. There is no mention of use cases, prerequisites, or conditions, leaving the agent without contextual selection criteria.

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

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