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FableCut

FableCut

by ronak-create
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Hybrid

fablecut_normalize_audio

Normalize audio clips to target LUFS or peak levels by measuring source audio and setting clip gain; linked stems share one gain for balanced mixes.

Instructions

Loudness-normalize clips: measures each clip's source audio (ITU-R BS.1770 integrated LUFS, or sample peak) after its channel routing and sets props.gain (clip gain, dB) so it lands on the target — the same measurement as the editor's Normalize button. Linked stems (a video's per-channel audio clips) are measured together and get one shared gain, so a stereo pair stays balanced; passing a video clip normalizes its stems. Volume keyframes / fades are untouched (they ride on top). Typical targets: -14 LUFS streaming/social, -16 LUFS podcast/dialogue, -23 LUFS broadcast, or mode 'peak' at -1 dBFS. Needs ffmpeg + ffprobe on PATH. Refuses locked clips unless force:true.

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": {
      "clipIds": "<clipIds>"
    },
    "name": "fablecut_normalize_audio"
  }
}

Input Schema

NameRequiredDescriptionDefault
modeNoMeasure integrated loudness (default) or sample peak
forceNoAlso change clips the user locked (only when they asked)
targetNoTarget level: LUFS for mode lufs (default -14), dBFS for mode peak (default -1)
clipIdsYesClips to normalize (audio, or video with audio)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv1.10.0

TDQS

A4.5/5.0
Behavior5/5

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

With no annotations, the description carries the full burden and does so richly: the measurement standard (ITU-R BS.1770 integrated LUFS / sample peak), that it writes props.gain in dB, that linked stems share one gain so a stereo pair stays balanced, that it refuses locked clips unless force:true, and that volume keyframes/fades are left untouched.

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

Conciseness4/5

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

A single dense paragraph that is front-loaded with the core action and wastes little, though the run-on style packs many clauses (stems, keyframes, prerequisites, locking) together. Every clause is informative, so it stays efficient despite its length.

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

Completeness4/5

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

For a 4-param mutation tool with no annotations or output schema, the description is nearly complete on behavior and prerequisites. The one gap is that it never states what the call returns (e.g., measured values), which the missing output schema would otherwise need it to cover.

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?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: target units depend on mode (LUFS vs dBFS), the force flag's intent ('only when they asked'), and concrete target values. It clarifies the mode/target interplay better than the schema alone.

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?

States a specific verb and resource ('Loudness-normalize clips') plus the exact mechanism (measures source audio, sets props.gain). An agent can instantly differentiate this from siblings like fablecut_denoise or fablecut_auto_duck, which perform unrelated audio operations.

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

Usage Guidelines4/5

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

Provides concrete usage context via typical targets (-14 LUFS streaming, -16 podcast, -23 broadcast, peak at -1 dBFS) and states a prerequisite (ffmpeg + ffprobe on PATH). It does not explicitly name a sibling alternative or state when not to use it, so it falls short of a 5.

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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