previous_track

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

The description conveys that this action changes the current media position, consistent with `readOnlyHint: false` and `idempotentHint: false`. However, it does not disclose edge-case behavior such as what happens if there is no previous track or whether playback state pauses/resumes.

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 one concise sentence that states the action and target resource without filler. It is appropriately sized for a no-arg media control command.

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 simple, parameterless tool, the description plus annotations provide enough context to invoke it. Additional details about return values or no-op behavior would be helpful but are not essential 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?

The tool has zero parameters and an empty schema, so there is no parameter semantics to document. The baseline score of 4 applies because no parameter information is needed.

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 'Skip to the previous media track.' clearly names a specific verb ('skip') and resource ('media track'), and the word 'previous' differentiates it from the sibling tool `next_track`. There is no ambiguity about what the tool does.

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 clearly implies the use case: go backwards in media playback. It does not explicitly name `next_track` as the alternative or mention edge cases like being at the first track, but the context is strong enough for an agent to select it appropriately.

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