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

Annotations already declare readOnlyHint=false and destructiveHint=false, so safety is covered. The description adds valuable behavioral context beyond that: the kit becomes project-wide in effect, and the default can be cleared by omission. It does not mention whether an existing default is replaced or what happens to previous settings, but it is materially more informative than the annotations alone.

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?

A single compact sentence with the core action front-loaded, followed by effect and clearing semantics. Every clause earns its place, including the brief 'Free' cost note.

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 mutation tool with annotations covering safety and no output schema, the description is largely complete: it covers purpose, project-wide effect, and clearing. Minor gaps remain around whether an existing default is replaced rather than cleared, and the role of project_id.

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%: stil_kit_id is documented in the schema, project_id is not. The description reinforces the omit-to-clear semantics for stil_kit_id but adds no meaning for project_id. Baseline 3 is appropriate for partial coverage where the schema already handles the documented parameter.

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 ('Set the project's default style kit') and explains the consequence ('runs in every image and clip of the project'). The clearing behavior is also stated, which distinguishes it from sibling tools like lab_create_stil_kit and lab_list_stil_kits without needing to name them.

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?

Clearly says when this tool is appropriate (to set a project-wide default) and how to clear it (omit stil_kit_id). It stops short of naming alternatives or stating exclusions, but the usage context is unambiguous.

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