library_stats

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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the tool's safety profile is well established. The description adds useful context about what metrics are covered but does not disclose any additional behavioral traits such as response size, potential latency, or how the library is determined. With annotations covering the core behavior, a score of 3 is appropriate.

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?

The description is a single sentence that packs specific, useful details into a compact statement. Every clause contributes meaning, and the structure is easy to parse. There is no redundancy or 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 parameters, strong annotations, and an output schema present, the description only needs to communicate what the tool reports, which it does comprehensively. It names the categories of information (totals, albums, named people, indexing, iCloud-only content) and leaves return format details to the output schema. Nothing essential is missing.

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?

The tool takes zero parameters, so the baseline for parameter semantics is 4. The description does not need to explain parameter meaning since there are none. The schema coverage is effectively 100% because the parameter list is empty, so nothing is left undocumented.

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 clearly identifies the resource (the library) and the specific kind of information provided (totals, albums, named people, indexing status, iCloud-only content). However, it lacks an explicit verb like 'get' or 'retrieve', so it describes the subject matter rather than stating the action, making it slightly less actionable than an ideal definition.

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 description gives no guidance on when to use this tool versus alternatives. While no sibling tool appears to perform the same function, the description does not state when this should be chosen, nor does it mention any prerequisites or context. It is left entirely to the agent to infer that this is the go-to for library-level statistics.

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