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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds real value beyond that: it discloses the exact return shape (first key idea full, other headings only) and, notably, that an unavailable title or language returns a soft 'opens soon' message rather than an error — a non-obvious behavior an agent needs to interpret results correctly.

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 sentences, front-loaded with the core return description before parameter guidance and the availability caveat. Some phrasing is awkward ('answers that it opens here soon'), but there is little waste.

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?

With no output schema, the description does the work of explaining what comes back (full first key idea with heading, other headings only) and how language affects returned text. It stops short of explaining pagination or whether the headings themselves are actionable, but nothing critical to a correct call is missing.

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 the enum lists every language code with names, so the schema carries the weight. The description adds only a little: it ties 'part' to choosing a key idea and implies part defaults to the first. 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?

States a specific verb and resource with scope: read the 15-minute summary of one title, returning the first key idea in full plus headings of the rest. That content shape distinguishes it from siblings like get_book_outline or get_chapter_summary, but the description never names an alternative explicitly, so an agent must infer the boundary.

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?

'Choose a key idea with part' gives usage for one parameter, and the note that unopened summaries respond that they will open 'here soon' implies availability handling. However, there is no explicit when-to-use vs. get_chapter_summary, get_book_outline, or get_book, and no stated prerequisites beyond the id.

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