playback_compare_states

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It openly states that this is a sidecar-only, API-free operation with zero API calls, and its 'Shows...changes' phrasing implies a read-only diff. This is useful context beyond the raw tool name, though it does not cover edge cases like missing snapshots or failure behavior.

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?

Two short sentences deliver the purpose, scope, compared dimensions, and a clear behavioral signal (0 API calls). The most important information is front-loaded, and there is no filler.

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 relatively simple tool with fully documented parameters, the description is complete enough: it explains what the tool does, the sidecar-only nature, and the dimensions it compares. It does not explain what 'sidecar' means or how to discover available playback snapshots, but those are minor gaps given the sibling list and schema.

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 input schema already documents all three parameters with 100% coverage, including descriptive text for state_a, state_b, and response_format. The description adds no additional parameter-level detail, so the baseline score 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 uses a specific verb ('Diff') and a specific resource ('saved playback snapshots'), and clarifies the scope with 'sidecar only, no API'. It names the exact fields compared (item/shuffle/repeat/progress/device/context), making the tool's purpose unmistakable and distinct from playlist snapshot diff tools.

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 communicates the operational context: this works on sidecar snapshots and makes zero API calls. This implies it should be chosen when the agent wants to avoid API usage, but it does not explicitly name alternative tools or state when not to use it, so it stops short of a 5.

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