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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description earns credit for going further: it discloses the return fields and, notably, the failure semantics — an unreadable entry returns `type: null` with an `error` rather than failing the whole listing. That partial-failure behavior is real context an agent could not infer from the annotations.

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 tight sentences, front-loaded with purpose and return shape, then parameter guidance, then failure behavior. Every sentence carries information and nothing is repeated from the schema or annotations.

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 covers the return fields itself, plus error handling, parameter selection and container semantics, against annotations that carry the safety profile. An agent has everything needed to call this correctly without opening anything else.

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 the baseline is 3, but the description adds meaning beyond the schema: it explains that `bundleId` targets the app's own container where an app under test keeps its database, caches and logs, and that `depth` above 1 triggers recursion. This gives the agent a reason to pick each parameter rather than just its format.

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 ("List files and directories on an iOS device") and enriches it with the return shape (name, type, size, mtime), making the scope distinct from a single-file stat or a search. However, it never names a sibling such as ios_file_find or ios_file_stat, so the differentiation is implicit rather than explicit.

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 clear conditions for the key choice: pass `bundleId` to browse an app's own container, omit it for the shared media directory, and use `depth` above 1 to recurse. It lacks explicit when-not guidance or a pointer to the alternative listing/search tools, so it is clear context rather than full routing.

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