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

Annotations already declare readOnly=false, idempotent=true, destructive=false, and openWorld=false, so the safety profile is covered. The description adds real value beyond that by disclosing the persistent side effect: kept pieces become kit pieces of the workspace and the artist, a state change in two scopes. It does not say whether that join is reversible or what permissions are needed.

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?

Short and front-loaded with the key branch, but the single sentence is a run-on with a missing clause boundary ('...planned from it save_to_kit true (default):') and a missing apostrophe, making it harder to parse than its length justifies. The content density is good; the structure is not.

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 2-required-param tool with no output schema and full annotation coverage, the description covers the one semantically opaque parameter. It leaves undefined terms ('kept pieces', what a lookbook must be in for the update to apply) and omits any return-value note, so it is adequate rather than complete.

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 50%: save_to_kit has no schema description at all, and lookbook_id only says 'The lookbook id'. The description compensates by defining exactly what true and false do for save_to_kit, which is the only meaningful ambiguity. It does not reconcile the stated 'default: true' with the parameter being required, which is a small gap.

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 explains the effect of the save_to_kit flag (kept pieces join the kit vs. video-only), which conveys the tool's purpose obliquely, but never states the core action ('update a lookbook's kit-saving setting') and never references how it differs from siblings like keep_music_video_lookbook_piece or redesign_music_video_lookbook. An agent could infer intent, but only after parsing a garbled sentence.

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 phrase 'when a video is planned from it' implies the lifecycle stage at which this is called, and the true/false branches give the decision context. However, there is no explicit when-to-use/when-not guidance and no naming of alternatives, so the routing signal is only implied.

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