now_playing

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

With no annotations, the description carries the full disclosure burden. It clearly indicates a non-mutating read operation ('Get') and specifies the observable fields included in the state. It doesn't mention edge cases like no active device, but for a zero-parameter read-only tool this is acceptable and the output schema likely covers response details.

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?

A single, front-loaded sentence that states the action and the specific state fields. No filler or repetition of schema information.

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 zero-parameter read-only tool with an output schema present, the description is complete. It tells an agent exactly what to expect from the tool and no further context is needed to invoke it correctly.

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 accepts no parameters, so parameter semantics are trivial. The schema coverage is 100% with an empty properties object, and the description adds no parameter details because none exist. Per rubric, a zero-parameter tool gets a baseline of 4.

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?

Uses a specific verb ('Get') with a clear resource ('current playback state') and enumerates the exact fields returned (track, artist, device, progress, shuffle/repeat). This clearly distinguishes it from control-oriented siblings like play and control and from list tools like get_queue and list_devices.

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 states precisely when to use the tool: to retrieve the current playback state. It doesn't explicitly name alternatives or exclusions, but sibling overlap is minimal since it is the only getter for live playback status. Context is clear even without explicit 'when not to use' guidance.

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