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

Adds a genuinely useful side effect not in the annotations: 'Opens the Music app when it is closed,' which matters for an agent running headless or in a staged workflow. Annotations already cover read-only/non-destructive, and pagination behavior is disclosed in prose, but there's no note on error behavior for an unknown playlist name.

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 tight sentences: the default behavior and return fields first, the mode switch second, pagination and the app-launch caveat last. No filler and the most decision-relevant facts 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?

With an output schema present, the description needn't document return shapes, and it still covers the dual-mode contract, pagination, and the app-launch side effect. Nothing needed to invoke it correctly 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?

Schema coverage is 100%, so baseline is 3. The description earns the extra point by clarifying that `playlist` accepts a name OR an id and that results come back in playlist order, and by explaining the two parameters are page controls applied to both list modes — semantics the schema alone doesn't convey.

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 (lists the playlists of the Music app) and enumerates the returned fields, plus a clearly described second mode when `playlist` is supplied. It implicitly separates itself from music_search_library and music_add_to_playlist, but never names or contrasts a sibling explicitly.

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 a clear conditional for the alternative mode: pass `playlist` (name or id) to get that playlist's tracks instead, in playlist order. What's missing is guidance on when this is preferable to music_search_library or how to discover a playlist name before calling.

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