What is playing

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

The readOnlyHint annotation marks the tool as read-only. The description adds a significant non-obvious behavior beyond the annotation: non-running players are reported as such and are not launched. This enriches the behavioral model, but it doesn't disclose potential error cases or return format, so a perfect score is not reached.

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?

Two concise sentences deliver the exact purpose and a critical safety note without any fluff. Every word earns its place, and the most important information is 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?

For a one-parameter, read-only query tool with no output schema, the description covers the feature set, edge-case behavior (non-running player), and the practical benefit (safe to call). Nothing important is missing given the tool's simplicity.

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%: the only parameter 'player' has a description ('Ask one player only. Omit to report both.') and an enum. The tool description adds no extra parameter details beyond what the schema already offers, so the baseline of 3 is used.

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 uses a specific verb ('Report') and details the exact data ('current track, artist, album, position, and playback state') for the two players, clearly stating the tool's scope. It doesn't explicitly contrast with sibling tools like hs_music_control or hs_media_control, so it misses the top score for sibling differentiation.

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 provides a useful usage hint: 'A player that is not running is reported as such rather than being launched, so this is safe to call as a plain query.' This implies it is a non-side-effecting query tool, but it never states when to pick this over alternatives. Usage context is implied rather than explicitly defined, so a 3 is appropriate.

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