Fade audio

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

Beyond the annotations (readOnly=false, destructive=false, idempotent=false), the description adds valuable behavioral context: video is stream-copied so only audio is re-encoded, and the fade-out is positioned from the file's measured duration. These are non-obvious traits that materially affect how the agent invokes and evaluates the 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?

The description is two short paragraphs, front-loaded with the core action. Every sentence earns its place: the first states the purpose, the second clarifies fade-out mechanics and the encoding strategy. There is no filler or redundancy.

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?

Given the tool's moderate complexity (nested encode options, 5 top-level params) and the presence of an output schema, the description is mostly complete. It covers the core behavior, the fade-out quirk, and the encoding approach. It does not explicitly mention output path defaults or encode option interactions, but those are already documented in the schema and are standard for this tool family.

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 high (80%), so the baseline is 3. The description adds meaningful semantic context for fade_out: it explains that you provide the fade-out length rather than computing a start time, because the tool measures from the file duration. This is beyond what the schema's 'Fade-out length in seconds' conveys. Other parameters are already well-documented in the schema.

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 opens with 'Fade a file's audio in at the start, out at the end, or both' – a specific verb and resource. It clearly distinguishes this from sibling tools like trim or normalize_audio by focusing solely on audio fades. The additional detail about fade-out positioning and video stream-copying further defines the tool's specific role.

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 intended use is clear: apply fades to audio. It implicitly tells you when to use it (whenever a fade-in/out is needed) but does not explicitly mention alternatives or exclusions. The tool's narrow name and description make the context obvious, though it lacks an explicit comparison to siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.