Get library item

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

The description adds significant behavioral context beyond the annotations (readOnlyHint=true). It discloses that the tool includes listening progress of the API key's user, and that the compact projection excludes chapters, audio files, and tracks. This goes beyond the standard read operation hint and provides valuable behavioral expectations.

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 only two sentences, with the first sentence immediately stating the purpose and included resources. The second sentence efficiently covers exclusions and alternatives. Every sentence earns its place with no redundancy or fluff.

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?

Given the tool's simplicity (two parameters, no output schema), the description is fully complete. It covers what the tool returns (metadata, tags, listening progress), what is excluded, and how to get the excluded data. The absence of an output schema is compensated by a clear description of the return content. The readOnly annotation is consistent.

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 has 100% coverage with descriptions for both parameters. The tool description adds value by explaining the behavior of the detail parameter (compact vs. full) and how it relates to excluding chapters/tracks. It does not repeat the schema description for library_item_id, which is already sufficient. The added context is useful but not critical.

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 'Fetches one book or podcast' and specifies the included resources (metadata, tags, listening progress). It distinguishes itself from siblings by explicitly mentioning get_item_chapters for chapters and detail='full' for everything. This provides a specific verb+resource scope and differentiates from sibling 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 provides clear guidance on when to use this tool (fetching a single item) and explicitly directs to alternative tools for chapters (get_item_chapters) or full detail (detail='full'). It does not explicitly state when not to use it, but the context of fetching a single item vs. listing or searching is implied. The presence of alternative tools enhances decision-making.

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