previous_track

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

No annotations are provided, so the description carries the full burden. It discloses the key behavioral nuance: the tool restarts the current track if playback is more than 3 seconds in, which is critical for the agent to predict the outcome. It doesn't mention other behaviors like whether it pauses or stops, but for a simple media control, this is adequate.

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 two sentences, front-loaded with the primary purpose, and the second sentence adds a crucial behavioral detail. Zero waste, perfectly concise.

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 the tool's simplicity (one optional parameter, no output schema, no nested objects), the description is complete enough. It covers the main action and the key edge case (3-second rule). It doesn't describe return values, but since there's no output schema, that's not required. The only minor gap is not mentioning what happens if there is no previous track, but that's a minor omission for a media control tool.

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 description coverage is 100% (the only parameter deviceId is described as 'Device ID (from get_devices). Uses active device if omitted.'). The description adds no additional parameter semantics beyond what the schema provides, so the baseline of 3 is appropriate.

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 the tool's purpose: 'Go back to the previous track.' It uses a specific verb ('go back') and resource ('previous track'), and the additional detail about restarting the current track if more than 3 seconds in distinguishes it from a simple 'previous' command and from sibling tools like next_track.

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 clear context on when to use the tool (to go back to the previous track) and includes a specific behavioral condition (if more than 3 seconds in, restarts current track first). It doesn't explicitly mention when not to use it or alternatives, but the context is clear enough given the sibling tools (e.g., next_track for forward).

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