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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile needs no repetition. The description contributes beyond that by disclosing sort direction and the exact returned fields (title, creator, media_type, status, rating, added date), which is meaningful behavioral context. It stops short of covering empty-result behavior or pagination beyond the schema's max limit.

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?

Three tight sentences: core behavior and ordering first, then example invocations, then the sibling disambiguation and return shape. No filler, and the most decision-relevant fact (addition order) is front-loaded.

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?

No output schema exists, and the description compensates by enumerating the returned fields. With only two optional, fully specified parameters and annotations covering safety, an agent has everything it needs to select and invoke this tool correctly.

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 coverage is 100% and both parameters (limit with min/max/default, media_type enum with default) are fully documented in the schema. The description never mentions limit or media_type, so it adds no meaning over structured data; baseline 3 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 verb and resource plus the ordering dimension ('List items by when they were ADDED to the library, newest first'). It also names the sibling it differs from (get_timeline) and how the orderings diverge, so the agent can distinguish them without opening schemas.

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?

Gives concrete trigger phrasings ('show me the last N things I added', 'my last 8 vinyl records') and an explicit exclusion: this is addition order, not reading/watching dates as in get_timeline. The when-to-use and when-to-prefer-alternative conditions are both stated.

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