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

With no annotations provided, the description carries the transparency burden. It discloses the return content ('LICENSE.json and AGENTS.md'), which adds value. However, it does not explain the nature of the download token, whether the URL is single-use, or any authentication requirements. The description is not contradictory but is minimal on behavioral details.

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 two short sentences, front-loaded with the core action and return info. Every word contributes, with no redundant or filler content.

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 one-parameter tool with no output schema and no annotations, the description covers the core function and return value. However, it is missing guidance on when to use this tool versus preview/chapter tools, and the token/URL terminology is inconsistent with the schema. It is adequate but not fully complete for an agent to confidently select it among many siblings.

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 schema description for download_url covers 100% of parameter semantics, defining it as 'The full download URL from the purchase response.' The description's mention of 'download token' is somewhat inconsistent with the parameter name, but the schema already explains the parameter clearly. No additional parameter guidance is needed, so baseline 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 states 'Download a purchased book' with a specific verb and resource. It distinguishes from siblings like get_book_preview and read_chapter by specifying 'purchased book' and 'download token', indicating a full-book download rather than a preview or chapter read.

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 implies usage context: you need a download token for a purchased book. However, it does not explicitly contrast with alternatives like read_chapter or get_book_preview, nor does it state when not to use this tool. It provides enough context for an agent to infer eligibility but lacks explicit guidance.

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