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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, yet the description still adds real value: the revert path via remove=true, the 60s cap, the lip-sync/length consequence, and the fact that the change isn't rendered and that regenerating spends credits. The only gap is it doesn't say what happens to a previously uploaded recording beyond remove=true.

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 purpose and effect before the parameter mechanics and the re-render caveat, which is the right order. It is dense – the opening sentence carries several clauses – but every sentence conveys a distinct, actionable fact with no repetition.

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 6-parameter mutating tool with no output schema, the description covers trigger, side effects, revert, prerequisites, credit cost and the required follow-up call on rendered videos. Nothing an agent needs in order to invoke it correctly is missing.

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%, so baseline is 3; the description still adds meaning the schema lacks – that audio_key and audio_upload_id are alternatives sourced from upload_audio/get_audio_upload_page, that narration is the transcript used to align text and visuals, and the 60s duration constraint. It stops short of stating which of the two audio parameters wins if both are supplied.

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 and resource ('Replace one scene's AI voice with the user's own recording') plus the resulting state (scene shows the person speaking, lip-synced, length = recording up to 60s). It is clearly separable from edit_scene_narration and regenerate_scene, which are the sibling tools an agent might otherwise pick.

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?

Gives explicit trigger conditions (AI voice mispronounces words, handles a regional language/accent badly, adds gibberish or stray sounds, and editing narration didn't fix it) and states the exclusion: nothing is re-rendered here, so on a rendered video use regenerate_scene(mode='narration'). It also names the prerequisite tools (get_audio_upload_page / upload_audio).

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