now_playing

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

The annotation already marks it as read-only, so the description need only add behavioral context. It includes the important conditional 'if playing,' which hints at potential null results, but does not explicitly state what happens when nothing is playing (e.g., returns null or empty).

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 short sentence that is front-loaded and contains no unnecessary words. Every part adds value.

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?

Given zero parameters and annotations, the description is mostly adequate. However, without an output schema, it is vague about what 'current track' means (e.g., just the name or full metadata). More specificity about the return value would improve completeness.

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 no parameters, and the schema coverage is 100%. The description adds no parameter information, which is acceptable as the baseline for a parameterless tool.

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 states it returns the current track in the Music app if playing, using a specific verb and resource. It distinguishes itself from sibling tools like music_playpause and music_next, which are actions, not queries.

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 wanting to know the currently playing track, but does not provide explicit guidance on when to use this tool versus alternatives like search_music_track. No exclusions or conditions are mentioned beyond 'if playing'.

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