tracearr_list_libraries

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

readOnlyHint is already true, so the description doesn't need to state read-only. It adds the specific content of the rollups, but doesn't disclose details like response format or pagination. This is similar to get_calls in the calibration, which received a 3 for transparency.

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 one concise sentence that front-loads the purpose ("Per-library rollups") and enumerates the key counts without waste. Every word contributes meaning, making it an excellent example of efficient specification.

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 an output schema and readOnlyHint annotation present, the description sufficiently covers the tool's functionality for an agent to select it correctly. It has no parameters, and the description clearly communicates the library-level scope, making it complete in context.

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?

There are zero parameters, so the description needn't explain any. The baseline for 0 parameters is 4, and the description doesn't need to compensate for any omitted schema info. It simply describes the output scope.

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 states "Per-library rollups" with explicit counts (item/movie/episode/show/track, total file size, per-resolution counts), making it clear this is a list/aggregate operation for libraries. It distinguishes from sibling tools like tracearr_get_media_stats by focusing on library-level rollups rather than per-media stats.

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 implies usage when library-level aggregate statistics are needed, but it doesn't explicitly mention when to use vs alternatives like tracearr_get_media_stats or tracearr_get_media. It gives no exclusion criteria, leaving the agent to infer the appropriate context.

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