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

No annotations are provided, and the description does not disclose side effects such as what happens if there is no previous track, whether playback state changes, or error behavior. The restart condition is mentioned but edge cases are omitted.

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, clear sentence with no redundant words. It efficiently conveys the primary action and a specific conditional.

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?

While the tool is simple, the missing parameter explanation and lack of edge-case handling (e.g., no previous track) create ambiguity. The expected output is not mentioned, but the main gap is the parameter semantics.

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 only parameter 'player' is a string with no description in the schema or the tool description. Its meaning (ID, name, etc.) is completely unspecified, leaving the agent to guess.

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 action: 'Go back to the previous track' with a specific condition 'or restart the current one, if it just started'. This distinguishes it from siblings like 'skip' and 'pause'.

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 gives a conditional for restart, but does not explicitly state when to prefer this over other controls or mention any prerequisites. It relies on implicit understanding of media controls.

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