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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered; the description still adds real value by disclosing the 90-second cap and the partial-result contract ('complete: false with the items finished by then'), and by clarifying the measurement semantics (allocated space, as du counts it). It does not mention behavior on unreadable or permission-protected folders, which is a minor remaining gap.

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?

Three sentences, each earning its place: the first defines the operation and output, the second the drill-down pattern, the third the timeout edge case. The scoping ('without changing anything') is front-loaded and there is no filler.

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?

With no output schema, the description carries the return-value burden and does so reasonably: ranked items, item sizes, folder total, and a completion flag. It is essentially complete for a 4-parameter read-only tool, though it leaves the per-item fields (e.g., name vs path) unspecified.

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%, so path, limit, deviceId, and workSessionId are already documented in the schema; the description adds only a loose implication of the path parameter ('in a folder', 'call it again on a large item'). Baseline 3 is appropriate when the schema does the heavy lifting and the description adds nothing parameter-specific.

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 ('Show what takes up disk space in a folder') plus the exact return shape: size of each item directly inside, largest first, and the folder total. This clearly separates it from siblings like list_directory, stat_path, and search_files, which enumerate or inspect paths but do not rank by disk consumption.

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 a concrete usage pattern: 'Call it again on a large item to look inside,' which tells the agent to drill down iteratively rather than expecting recursion. However, it names no alternative sibling (e.g., list_directory or stat_path) nor any condition under which this tool should not be used, so it stops short of full routing guidance.

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