video_mix_audio

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

With no annotations the description carries the full burden and does so well: it discloses the encode strategy (single AAC encode, stream-copy picture), that tracks sum without loudness normalization and may clip, that source audio is retained unless keep_source=false, that duration and relative timing are preserved, and that execution is synchronous in a worker thread with no background job or governed audio-bed receipt.

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?

Front-loaded with the core operation, then parameter format, then behavioral caveats. Every sentence carries information (clipping warning, keep_source, threading model), though the 'no governed audio-bed receipt' clause is slightly opaque and the density is high.

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?

An output schema exists so return values need no explanation, and the description covers the mutation semantics, audio mixing behavior, and execution model. Only the path/bitrate parameters remain unaddressed, which is a minor gap for an otherwise complete picture.

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 compensate. It documents the complex 'sounds' parameter thoroughly (path, start in seconds, volume as linear gain, fade_in/fade_out in seconds) and explains keep_source behavior, but input_path, output_path, and audio_bitrate are left unexplained beyond what their names imply.

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?

States a specific verb (mix) and resource (timed sounds into the primary picture) plus the encoding strategy ('one AAC encode and stream-copy the primary picture'), which differentiates it from a plain re-encode. It does not name a specific sibling (e.g. video_add_audio or video_add_generated_audio) to contrast against, so sibling differentiation is implied rather than explicit.

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 when-to-use/when-not guidance and no alternatives named, despite many overlapping siblings (video_add_audio, video_add_generated_audio, video_normalize_audio, sound_mix_render). The closing 'Listen before publishing' hints at a QA context but is not a usage rule.

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