Adjust a Premiere Pro track’s Audio Track Mixer fader in decibels, up to +6 dB, by specifying its 0-based index. Use it to balance or correct track levels in a timeline.
Set the Audio Track Mixer fader of a track (dB, max +6)
| Name | Required | Description | Default |
|---|---|---|---|
| volumeDb | Yes | ||
| trackIndex | Yes | Track index, 0-based (V1 = 0, A1 = 0) |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations cover the tool, so the description carries the full behavioral burden. It usefully discloses the unit (dB) and the ceiling (+6), but says nothing about permissions, whether the change is undoable, interaction with track automation, or what happens when a value above the maximum is supplied.
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?
A single short sentence, front-loaded with the verb and target, with the two most important constraints (unit and cap) parenthesized. Nothing is wasted.
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?
For a two-parameter mutation tool with no annotations and no output schema, the description covers the essentials of what is affected and the value semantics, but omits error behavior, whether out-of-range values are clamped or rejected, and any confirmation of what is returned.
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?
Only trackIndex has schema documentation (0-based, V1/A1 = 0), leaving volumeDb's units and bounds to the description, which supplies them: dB with a max of +6. The description therefore compensates well for the 50% coverage gap, though it doesn't clarify the meaning of 0 dB or a negative range.
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 ('Set') and a specific resource ('Audio Track Mixer fader of a track'), which distinguishes it from clip-level siblings like set_clip_volume and get_track_volume. It stops short of naming the sibling it complements or contrasts with, but the track-level scope is unambiguous.
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 description offers no guidance on when to use this tool over alternatives such as set_clip_volume, set_clip_channel_volume, get_track_volume, or set_track_muted, and it states no prerequisites like whether the track must already exist or be targeted.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.