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TMHSDigital

Screencast MCP

by TMHSDigital
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TypeScript
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music_bed

Adds background music to a video by looping or trimming it to the video length, applying fades and volume, and mixing or ducking it under existing audio.

Instructions

Lay a music track under a video: the music is looped/trimmed to the video length, faded in and out, and leveled. When the video already has audio the two are mixed, optionally ducking the music under the original. The video stream is copied; only audio is re-encoded.

Input Schema

NameRequiredDescriptionDefault
duckNoDuck the music under the original audio via a sidechain (default false).
musicYesPath to the music audio file (looped/trimmed to the video length).
videoYesPath to the video.
fadeInNoMusic fade-in seconds (default 1).
outputNoOptional output path. Defaults under SCREENCAST_HOME/edits.
fadeOutNoMusic fade-out seconds (default 2).
overwriteNoAllow replacing an existing file at the output path (default false).
musicVolumeNoMusic level 0..1 (default 0.25 over existing audio, 0.8 alone).

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.32.0

TDQS

A3.8/5.0
Behavior4/5

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

With no annotations, the description carries the full burden and does well: it discloses loop/trim, fades, leveling, mixing/ducking, and that video is copied while audio is re-encoded. It omits overwrite/output-file semantics and return behavior, so not exhaustive.

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?

Three tightly packed sentences, front-loaded with the core action and mechanics, with no filler.

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 an 8-parameter media-editing tool with no annotations or output schema, the description gives enough behavioral context to call it correctly. It could say more about output/return behavior, but the schema covers parameters.

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

Parameters3/5

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

Schema coverage is 100%, so parameter defaults and meanings are already documented. The description reinforces concepts like ducking, fades, and leveling but adds little parameter-level detail beyond the schema.

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

Purpose4/5

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

The description names a specific operation (laying a music bed under a video) and details its mechanics, so the agent knows exactly what it does. It does not explicitly contrast with sibling audio/video tools, so it stops short of 5.

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

Usage Guidelines3/5

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

It implies the use case (adding music to a video) but offers no explicit when-to-use/when-not or alternative tools such as normalize_audio or assemble_highlights. The condition of existing audio is behavioral, not usage guidance.

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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