play_previous_track

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

No annotations exist, so the description carries the full behavioral burden, yet it discloses nothing about what happens at the start of history (does it restart the current track or no-op?), whether it changes playback state, or whether history is a stack that gets consumed. An output schema exists, which relieves the description of explaining return values, but the runtime behavior of the navigation itself is undocumented.

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 nine-word sentence with zero filler, and the operative concept ('previously played track') lands immediately.

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 playback action with an output schema, the description covers the core intent, but the boundary condition that matters most for a back-navigation tool (no prior track available) is unstated. Adequate, with a clear gap around edge-case behavior.

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 takes zero parameters and the schema is empty, so there is nothing for the description to disambiguate. Baseline of 4 applies.

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?

States a specific action (go back) on a specific resource (the previously played track), which an agent can distinguish from skip_to_next_track by the word 'previously'. No sibling is named explicitly, so it stops short of full differentiation.

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 when-to-use is only implied: an agent must infer from the name and the phrase 'previously played' that this is the counterpart to skip_to_next_track. There is no explicit statement of when not to use it, no alternative named, and no mention of how it relates to resume_music or play_search_result.

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