Add background music under a video timeline’s main track, with auto-ducking to lower it during speech plus configurable start, volume, duration, and fades.
Lay background audio under the main track from timeline time start.
duck=True lowers it automatically whenever the main track has sound (speech).
| Name | Required | Description | Default |
|---|---|---|---|
| duck | No | ||
| start | No | ||
| src_in | No | ||
| volume | No | ||
| fade_in | No | ||
| project | Yes | ||
| asset_id | Yes | ||
| duration | No | ||
| fade_out | No |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are supplied, so the description carries the full burden. It adds real value by explaining what duck=True actually does (automatic level reduction under speech), which the bare boolean does not convey. However, it says nothing about mutability side effects, whether the new layer coexists with existing music, permission requirements, or what the call returns, leaving meaningful behavioral gaps for a mutation tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two tight sentences with the core operation front-loaded and the duck behavior second. Nothing is redundant or padded.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Nine parameters, no annotations, no output schema, and no schema descriptions mean the description should do much more. It explains only start and duck, leaving the source offset, duration-null semantics, volume scaling, and fade defaults undocumented, which is not enough for an agent to call this correctly without guessing.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0% across nine parameters, so the description must compensate. It clarifies two critical parameters: `start` as a timeline position (not a source offset) and `duck` as automatic ducking under main-track audio. That distinction between timeline time and source-in is genuinely useful. But `src_in`, `duration` (including the null default), `volume`, and the fade parameters remain entirely unexplained in both schema and description.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description gives a specific verb and resource: lay background audio under the main track, starting at a timeline time. That clearly separates it from siblings like add_clip or remove_music, though it doesn't name those alternatives explicitly.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The purpose implies the usage scenario (adding a music bed under existing audio), and the duck note hints at the speech-overlap case. There is still no explicit when-to-use or when-not guidance, such as pointing to remove_music for removal or import_media for getting the asset in the first place.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.