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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds real value beyond that: it discloses that the tool returns raster output ('Read the returned pixels') and that audio lanes produce a spectrogram plus a sound summary. It doesn't cover output size, cost, or pagination.

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?

Four short sentences, front-loaded with the purpose and followed by the most decision-relevant instruction (audio modes) before the usage trigger. The audio sentence partially duplicates the schema's own audio description, which costs a little.

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 two-parameter read tool with full schema coverage and no output schema, the description supplies purpose, usage context, and a return-format hint ('timestamped contact sheet', 'returned pixels'). Nothing essential to correct invocation is missing, though framing/resolution details are absent.

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 100% and both parameters are documented in rich detail (including null semantics and the mix/tracks/none meaning), so the schema does the heavy lifting. The description only restates that you can 'pass audio mix or tracks', adding no syntax or defaults beyond the schema. 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?

States a specific verb ('Look at' / preview) and a concrete resource ('a timestamped contact sheet of the entire composed timeline'), which implicitly distinguishes it from preview_frame and preview_range by scope. It never names those siblings explicitly, so differentiation is left to inference.

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?

'Use after visual, timing or sound edits' gives a clear triggering context, and the audio mix/tracks instruction tells the agent which argument treats which situation. No alternatives or exclusions are named, so it stops short of a 5.

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