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

Beyond the annotations it discloses a lot: the sheet is drawn into the workspace (explaining why readOnlyHint is false), returns per-moment flags for black frames and overlaps, is explicitly approximate (fonts, caption looks, animations differ from the export), and is free within the workspace quota. Cost model, fidelity limits, and side effects are all surfaced, consistent with idempotentHint=true and destructiveHint=false.

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?

Purpose is front-loaded in the first clause and the whole description is roughly 80 words with little padding; each sentence carries distinct information (scope, parameter meaning, returns, timing, caveats, cost). The bare "at: ..." fragment is slightly rough but readable.

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 an output schema, it covers what the agent needs: what is produced, when to call it, parameter modes, limitations, and cost. The only minor gap is that it does not identify the alternative when only raw timeline data (rather than a visual sheet) is wanted; return-value detail is rightly left to the output schema.

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 the baseline is 3, but the description earns above baseline by explaining semantics the schema does not: "cuts" means just before/after every cut plus each clip's middle, and "every:N" means every N seconds. It largely restates the list form and the 12-moment cap, so it is helpful but partly redundant.

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 states a specific verb and resource: produce an approximate preview sheet of the timeline composited from main clip, B-roll, text and captions at up to 12 moments. That is far more concrete than a tautology and clearly distinct in kind from data-oriented siblings such as video_project_get, but it never names a sibling or contrast case, so it falls short of full 5-level differentiation.

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?

It gives explicit timing guidance: "Review after each build pass and before exporting," which anchors the tool between video_project_edit and video_project_export in the workflow. It does not name an alternative or state when not to use it, so it stops at clear context rather than full when/when-not coverage.

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