analyze_disk_usage

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

The annotations already declare readOnlyHint=true and openWorldHint=false, and the description's 読み取りのみ is consistent with them rather than contradictory. It adds genuinely useful behavior beyond the annotations: the fixed category buckets and the caveat that entry sizes include their subtree, so parent and child sizes overlap. It says nothing about cost, performance, or traversal limits (e.g. symlinks, permission errors, unreadable dirs), which matters for a filesystem walk.

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 with no filler: purpose, then payload contents, then the size-overlap caveat, then the drill-down workflow. The most decision-relevant facts (what it returns, and that sizes double-count across levels) are front-loaded.

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?

An output schema exists, so the description doesn't need to enumerate return fields, and the annotations carry the safety profile. Given only two parameters and high schema coverage, the description is nearly complete; the only gap is the absence of any note on error or edge behavior (inaccessible paths, symlinks, large trees).

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 both parameters are already documented in the schema (including max_depth as 1=直下の子のみ and target_path as an absolute path allowing ~). The description's mention of max_depth and of reusing a discovered path adds only light framing on top of that. Baseline 3 applies when the schema carries the parameter documentation.

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 opens with a concrete verb+resource: it returns a capacity breakdown (容量内訳) for a specified directory, and explicitly notes 読み取りのみ. It also states what the payload contains (カテゴリ別合計 dev_cache/video/log/other plus top entries by size). It does not name or contrast with its siblings (scan_cleanup_targets, get_os_env_paths), so differentiation is left to the reader.

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 final sentence gives concrete operational guidance: after finding a large path, call again with that path to drill down efficiently, describing an iterative workflow. It gives no explicit when-not-to-use rule and never names an alternative sibling tool for the cleanup/environment-inspection case.

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