mix_narration

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

With no annotations provided, the description carries the entire transparency burden and meets it admirably. It discloses full-level voice, untouched video stream copying, bed mixing with LUFS offset, side-chain ducking, output duration behavior with padding/trimming, and ffprobe verification. This is far richer than a typical generic description.

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 compact yet information-dense, with the lead sentence capturing the essence and every following clause adding a distinct behavioral or parameter detail. There is no filler or redundancy; the 'ffprobe-verified' tag is a concise way to indicate reliability.

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 tool with moderate parameter count and no annotations, the description is remarkably complete. It covers the full workflow, parameter meanings, output timing behavior, and edge cases (shorter/longer audio). The existence of an output schema means return value documentation is not required, so no major gaps remain.

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%, so the description must explain the parameters, and it does. It clarifies bed_path as ambient/music, bed_below_voice_db as LUFS level below the voice, and implicitly ties voiceover_path to the primary audio. It also defines the relationship between video time and output audio length, covering the output_path semantics.

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 a specific verb and resource ('Lay a voiceover as the PRIMARY audio over a (silent) video'), making the tool's core action unmistakable. It goes further by explicitly positioning itself as 'the inverse of mix_music_into_video', which clearly distinguishes it from a closely related sibling.

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 states the ideal use case (voiceover as primary audio over a silent video) and implies a when-not-to-use case by contrasting with mix_music_into_video for videos that already contain speech. This gives the agent an explicit alternative and a clear decision boundary.

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