Apply fade-in and fade-out volume keyframes to an audio clip, optionally setting the audio level between the fades.
Fade an audio clip in and/or out with volume keyframes
| Name | Required | Description | Default |
|---|---|---|---|
| fadeIn | No | Seconds | |
| fadeOut | No | Seconds | |
| volumeDb | No | Level between the fades (default: current) | |
| clipIndex | Yes | Clip index on the track, 0-based from the left (see get_timeline_clips) | |
| trackIndex | Yes | Audio track index, 0-based (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 are provided, so the description carries the full burden. It implies a keyframe-adding write operation but does not state whether existing keyframes are replaced, what happens when fadeIn/fadeOut are omitted, or whether the change is undoable; for a mutation tool this is a significant gap.
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 front-loaded sentence with no filler. It is efficient, though its brevity leaves the behavioral gaps noted elsewhere rather than being a conciseness problem.
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?
Five parameters, no annotations, and no output schema: the description should disclose keyframe side effects, interaction with existing volume levels, and error conditions. It says nothing about these, leaving the agent guessing about consequences of the call.
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 coverage is 100%, with units, 0-based indexing, and the volumeDb default ('current') already documented. The description adds only the notion that fades are independently optional ('and/or'), so the baseline 3 is appropriate.
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?
Uses a specific verb ('Fade') and resource ('an audio clip') with a qualifier ('with volume keyframes') that distinguishes it from plain volume-setting siblings like set_clip_volume. It does not explicitly name an alternative sibling, but the operation is identifiable without opening the schema.
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?
No statement of when to use this over set_clip_volume, set_clip_channel_volume, add_keyframe, or apply_transition, and no prerequisites such as requiring an audio clip. The mention of 'and/or' only hints that each fade is optional; usage is left to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.